OP here,m thanks to everyone for the replies, I also been lurking in other threads over the past couple of weeks and so I have a much clearer idea of what I want, what I actually need, what I am capable of doing and not doing etc and I came up with a solution that I feel is the best option for me.
I've ordered a pretty decent bicycle, one that ticks all the right boxes for me - reasonably priced, light but strong frame, very good hydraulic disk brakes, good on and off road etc and after a lot of searching online, reading reviews and scouring ebike enthusiast forums I came up with the Specialized Sirrus X 3.0.
I decided against the 1000w/250w wheel hub motor with throttle set up and going for a 500w pedal assist only mid drive, I made the choice after reading posts here, elsewhere and researching online, i also decided not to attempt fitting it myself, instead I'm sending it to a company that does the conversion for you, it'll cost a little more but for me the knowledge it was fitted by people who know what they're doing, will come with a full warranty etc, is worth the cost, I already spoke to them and they've done a few conversions on this very bike and say it's ideal for the job, they also do a full service on the bike, adjusting brakes and gears if necessary, so when I get it back it'll be in just about the best shape possible, certainly better shape than if I'd tried all of this myself.
The total cost including all fees etc will be £1780, for that I'll get a brand new light and well balanced ebike with great stopping power. To get a ready made ebike with similar specs, similar power to weight ratio etc would cost well in excess of £2000, the closest I found was something like the mid range Cube bikes, but they start at the £2300 mark, of course there are some advantages with those bikes being specifically designed with the motor and battery fully integrated, the advantages certainly don't justify an extra £5-£600 for less power and range