Thank you Alison for posting these pics for me. I have idenitified this as Hylocereus undatus.
I also have another which has four sides to it and about as thick as a stick of licorice. It also has a white flower and flowers at night.
Have another I picked up yesterday which is flat but looks like a fish skeleton. any help would be appreciated thanks Jancc

Hi Jancc,
the night flowering cactus is probably
Epiphyllum oxypetalium "Queen of the Night".
The ones pictured above I used to grow in Perth.
I planted some against a paling fence and they climbed it!
The sent out aerial roots that attached to the fence to stabilise themselves.After a couple of years they were around 2 metres high.

Rosie (cimmaron), I have looked up the descriptions of Epiphyllum and Hylocereus in 'The Cactus Family' (Anderson 2001). Epiphyllum always has the stem tips flat; the floral tube is long, curved and very thin. Hylocereus has 3-angled stems (though I think they can throw some with 2 or 4 angles); the floral tube is relatively short and thick, almost absent in some species judging from the illustrations. So I would say Jancc's plants look more like Hylocereus. H. undatus in my experience will grow up trees or brick walls clinging by its roots like ivy, sometimes to heights of over 10 m. I don't think epiphyllums do anythging like that. Where I have seen E. oxypetalum it makes a multi-stemmed shrub about 1.5 m high, though maybe it can get a bit taller.
As for 'epiphyllum hybrids', it's interesting to note what Anderson has to say: "One encounters numerous so-called epiphyllum hybrids, which in fact rarely involve species of Epiphyllum as a parent. Rather, these magnificent plants, bearing shimmering, iridescent flowers, are mostly hybrids of related genera such as Disocactus, Pseudorhipsalis, and Selenicereus."

Sorry Sandie for being dyslexic and calling you Rosie.

Tony thanks, as I was the original poster I've forwarded on your response in case not read. As my late father used to say "call me anything just don't call me late for dinner"

Probably Hylocereus undatus....
Cheers Sue

Hi Folks
thanks for all the info. Hylocereus undatus takes the cake. found it in a book. i think they use this also for grafting on those pink and yellow blobs. anyway they had that in a nursery i went to yesterday.
have this other one which i think is Epiphyllum guligerum (fishbone cactus). this was listed in a book but no photos.
also have got another one. it's about as thick as a straw and looks like someone has twisted it. only have a cutting so don't know how big it will go.
any suggestions on good books to buy. i may put in a request for this one on another posting.
cheers Jancc

re the fishbone cacti. found it on pk'scacti&succulentpages. it's a cryptocereus anthonyanus, if anyone is interested.