I'm sure you've seen this but here's the Sussex Site.
http://www.sussex.police.uk/recruitment/pc_mai n.asp
Training from Force to Force differs but it's becoming more common for a short 5 week theory and street skills course prior to extended on-the-job training with tutor constables which includes continuation legislation training.
This site is a national site which gives info about the job and questions/scenarios to assess how you'd approach different situations...
http://www.policecouldyou.co.uk/officers/overv iew.html
Initial pay is about �20500 pa but dependant on your location you may get more in allowances.
Why not contact your local station and see if they'll let you go out for a shift with some officers - I did that before I joined and really enjoyed it.
If you go for it, good luck. You'll work with some great people and see things you'd never see anywhere else - just be prepared for the downside of the job too though - it's not, by any means, non-stop action and fun - but I've enjoyed it and still do. As long as you have more good days than bad then it's worth continuining with it.