True. It is all in CAP 413. But my advice is:
1. Don't give your life history on initial contact. Something like "Liverpool, this is G-ABCD" should suffice; they'll then tell you to standby, go-ahead or contact them on another frequency. Know how to acknowledge that - without getting too bogged down in the 'wun too tree daysimal fower fife' business.
2. If told to go aheead, just tell them:
Who you are: G-ABCD, PA38 from Welshpool to Liverpool.
Where you are: Approaching the Scousetown VRP at 2500ft on 1016
What you want: Request Flight Information Service
They will then ask for whatever else they need.
Above all, keep it simple, note the microphone technique described in CAP413 and the relevant safety leaflet - and if you don't understand what they say, don't be afraid to request them to "Say again".
Congratulations on your very commendable intention of getting ahead of the game to prepare yourself for your next lesson!