What’s your budget on the bike?
well all in jacket, trousers, boots, gloves, helmet, bike, provisional test and cbt around £2000 at the very very most would prefer cheaper oh and insurance as well!
I think you want to work backwards for your budget - check what insurance quotes you get on Confused.com, CBT will be about £100 I think.
Make sure you get decent waterproof gear (although kevlar jeans are nicer to wear when it’s hot than waterproof trousers) with armour at the knees, elbows and shoulders - maybe £300 would get you a decent basic set of everything, you can always search ebay for bargains but you should get a new helmet. Removable waterproof/thermal linings and vents in jackets/trousers will make your gear more versatile for the changing british weather.