Hi Mandy, I'm certainly not an expert and most of whatI bring in are cuttings to start new plants and winter those over. But when I do bring in pots I usually wash off the plants with a sprayer attached to a garden hose. Then I bring them in and keep them in a separate room from my other plants for a week or two. After that if I don't see any signs of "hitchhikers" I bring them in with my other plants. If I do have to spray them I'll usually try an insecticidal soap. I would think that any nursery or most other places that sell plants would carry those items too. Hope this is some help.

I wouldn't use any extreme chemicals unless it is really necessary. Hostaholics advice is on the money. Any serious infestations would be the only reason I would use a systemic.

I agree with the above. Your best bet is to start early and just handle a few at a time. Look each over thoroughly (under the leaves, along the stem - especially nooks and crannies where the petioles meet the stems, scuff up the surface of the soil a little & check it out), then give each a rinse with a garden hose or sprayer, upper and lower sides of leaves.
If you feel better about using something just in case some critters escape your attention, you could use an insecticidal soap. I don't know what brands are available where you live ("Safers" is popular in the US), but if you ask for insecticidal soap in your local garden center, they'll be able to point you in the right direction.
Neem oil is another insect deterrent that's not toxic to most other life forms (including beneficial insects like bees). It's also a fair fungicide. Again, that's a product name (neem oil), not a brand name, so you could ask for it locally.
Water with regular soap, not detergent or antibacterial, sprayed all over the plant helps prevent or get rid of mites and some other pests, too. Rinsing the next day helps keep soap residue from attracting dust.
If you've left pots sitting on or near the ground, they might have critters that have crawled up the pots' drainage holes. Most of the large soil critters, and some of the small ones (like springtails) won't cause much if any harm to your plants, but you don't want millipede explorers, or earthworms crawling out and drying up on your floor, so best to leave them outside :) Setting the whole pot in a bucket of water for an hour will help chase out some soil critters. (water level just barely below pot rim level -- check for critters on the surface & get rid of them) It might encourage fungus gnats later, but no system is perfect. *sigh* Also, be careful with cacti, as you don't want the pots overwatered, especially when the temps are cool! Only soak them if their mix has perfect drainage and if it's warm where they'll be until they dry out.
If you see pests like scale or mealy bugs, regular isopropyl alcohol spritzed from a hand-held sprayer can help get rid of them. It takes regular applications over 2-3 weeks to make sure you get them all. I've used 70% alcohol straight as is from the bottle on a very wide variety of plants with no ill effects (to the plants!) but I'll follow the trend of caution in what I recommend to others -- you might want to just spray a leaf or two leave it a day or so and make sure the plant isn't damaged from it. ...and of course, be sure not to breathe the mist in when you're spraying.
I go the non-toxic (or low-toxicity) route first, but rather than risk my whole collection, I will resort to using a systemic when I feel it's needed. Using a granular form is safer, IMO, as I don't have to worry about what surfaces are being hit with overspray, or whether I'm breathing it or getting it on my skin. I just dig a little hole in the potting mix, put in a small amount of the granules, and cover it back over. (Follow directions carefully, and go easy on the water the first few times you water afterward.) The most popular chemical of the moment is Imidicloprid, because it has fairly low toxicity to mammals. Once again, that's the name of the chemical, so you could ask for it locally & knowledgeable folks could let you know under what brand/s it's sold in your area.
We'd have no reason to lose patience; you ask good questions and give lots of background info to explain your questions! Questions and answers are a big part of the purpose of the forum :) Best of luck!

Wow thank you all so much for your great advice...how wonderful are you all!!
ooojen,
thank you so much for taking the time to explain all of that to me, you have been a really big help, thank you! I know it all sounds so simple, but a lot of the time I just end up totally confused, as I haven't a clue about the products you are all talking about!
In the USA you have so many fab things, that I'm never likely to find here :(
But now you have explained it all in great detail, i am much clearer & shall see what products i can find on e-bay incase. See, i never knew you could get an insecticidal soap! (just had a vision of lots of little bugs, using their little bar of soap in the tub!!)

Who knew that putting plants outside isn't just that simple. being the first year, i never even thought of the bugs that could come in, until a couple of months ago it dawned on me!
Ohh, no dried up earthworms in the carpet for me...bad enough finding mini dried slugs the dogs have bought in on their paws...yuck!!Even caught a snail one week that was happily making it's way across the living room carpet...that is the trouble with having patio doors right in the living room, the wildlife think it's an open invitation to come on in!

Thank you once again, for all the advice, it's much appreciated:)
Wish me luck!

Hugs,
Mandy (UK)