One way is to use standoffs. Most often they resemble a hex nut but come in various heights. They can be had in metal or nylon. Radio Shack and most other electronic places have them. I have a bag of surplus ones from Electronic Goldmine that were affordable.
Here are some examples from the Maplin site: **broken link removed**
Here is a list of some Maplin stores near(ish) to you: **broken link removed**
Note that I've never bought electronics in the UK. I haven't even been there since 1992. Many forum members are from there though so they may have better ideas for you.