Hi Moto,
Not sure about UK suppliers, but in Oz I can get self adhesive nylon standoffs:
They have a small piece of double sided tape on the base, and provide a really firm bond to plastics.
Farnell have some similar products, though they are not the cheapest bunch to deal with. I can buy this sort of component from small electronics retailers, who usually have a much better price than Farnell or RS. I don't know of any small players in the UK market though. I would generally only go to Farnell or RS for hard to find parts, due to their high pricing.
Be careful to match the hole size with the standoff. A lot of PCBs use M3 mount holes, while a lot of nylon standoffs are made for M4.
