Sorry to hear of your frustration. I don't know if it's any less frustrating for you to hear that you should go digital whilst you're broke either. And digital cameras have their own problems when trying to cope with long exposures in the cold night, as well as signal:noise problems. Guess you don't need to be frustrated even more from hearing that buying bigger and better equipment doesn't make a better photographer either.
Here goes (me trying to be helpful-unhelpful):
--------------------------------------------------------------------------------
"i picked up a film today of what i imagined would be some great photos taken of london a few nights ago. i am happy with about 2 maybe 3 of them out of 36."
Did you keep a record of exposures to check against the images?
"most of the shots i took came out grainy and it was fuji realia 100 iso which is suppose to be fine grain!"
It is fine grained. You can get beautiful enlargements from it, if you
a) expose the film correctly
b) scan and print correctly
I've never liked Jessops much. Before I could afford a pro-lab, I enjoyed using Peak Imaging. You might check them out. Their quality is more consistent than Jessops, and they also offer a higher end service for prints too.
If you underexposed the prints, then the grain will show up when the mini-lab operator tries to bring the neg into a printable image. Depending on the quality of the scan, you might be better doing your own maybe. Scanning your own images might be one way to go? You might be able to milk more out of a negative than the automated digi-lab once you have a few photoshop basics.
" i shot on various apertures and speeds and still got awful results. ggrrr!"
Again, it doesn't help unless any of these are fairly accurate exposures and are also printed with the correct density. If a mini-lab is the budget you have, and you feel like you're wasting money getting mini-lab prints, maybe saving the money up for a scanner and scanning the images which work for you will reduce your expenditure on wasted prints. I've never been particularly happy with mini-lab attempts of 'night photography' work except when shot on tungsten slide film or black and white negative and output via the mini-lab. Of course, a quality colour C41 lab could turn out a great print.
Fuji Superia, although not as specialised as Fuji Reala is a great colour film for night time shooting.
Best of luck.