Really depends on a few factors:
-- photographer's experience and any accreditations they hold eg WPJA
-- the job - is it bride getting ready 'til first dance affair? Or just the service and reception, or...? Some photographers will do a package, some will charge by the hour
-- end package - do you get a website? A photo album? A couple of dvds to archive?
-- where in the UK you are (and also if the photographer you've picked has to travel)
Whilst wedding photographers seem terribly expensive, from the other side of the fence - a good photographer will be on her toes all day, and not miss a single crucial (eg first kiss) shot, or informal or unexpected shot that'll help tell the story of the day. It's relatively risky, hard, tiring work. As others posters have expressed their disappointment at their photographer's work - it's work that, if you're conscientious, you simply can't get wrong, eg camera fail, missing crucial family shots etc.
I've done friends of friends photos in the past, when I wanted to change career. I started charging around £100 an hour (London only) for reportage. There are some rather old albums here:
www.flickr.com/photos/handfulofconfetti/collections/72157619124963421/
The £100 an hour covered my time, my equipment, travel, hours of editing of photos, eg cropping, retouching, website and 2 DVDs.
When looking for a photographer, I'd say look for someone who seems very calm (I ended up doing a bride's hair once, seriously, when the hairdresser failed to turn up), who's genuinely interested in this type of photography, who really delves into and understands what you want, who's interested in learning about your family and any nuances within it (eg, people who might refuse to be in photos with other family members - it does happen - and how to work around that).
If you want formal photos, eg family members lined up, then don't pick a reportage photographer, and vice versa - the skills are really quite different. It should be clear from their portfolio what shots they're actually best at taking.
And this is a friend of my DP - who I'd love to use, should I ever get the chance =)
www.markwallisphoto.com/
Good luck, and congratulations!