hi SNAZ,
interesting, I also live in england and am similar age to you.. ok heres my advise..
for a decent starter all in one kit.. I would recommend the papamotor kit, theres quite a few users of this kit in these forums, and EBIKEFL will be very happy to help you as he is an expert on this kit.. the battery they supply is high end ping battery, very good reputation...
you can buy the 32 mph kit for around £675 with everything you need..
there are two types of hub motors geared and direct drive.. geared are more smoother at low speeds and have no magnetic resistance, they however have more parts and need to be taken care of highly.. but still a good geared motor like a BMC version 2 or version 4/ or MAC motor can get up to 10,000 miles or more if you look after it well..
a direct drive motor is more simple construction and more reliable, however they have magnetic resistance that is when not peddaling there is a slight drag ( cogging) , but they generally last longer, and a good direct drive motor can be modded and over volted leading to insane speeds like 50 mph plus.. I think the record is over 80 mph..
if you dont go for the papamotor kit, then I would suggest buying some thing more expensive like BMC geared motor from Ilia at ebikessf.com or a MAC motor from a guy known as cellman.. he is british but lives in china..
ebike.ca have a geared ezee motor and also crystalyte direct drive motors.. the owner of ebike.ca is Justin and he runs the endless sphere forum..
geared motors have the advantage also of being half the weight of a direct drive and also much smaller, so much more stealthy..
from your specification it seems to me that your describing the papamotor kit..
PAS, pedal assist
up to 20 mile plus range
up to 32 mph
top battery
all in one kit
£675 for everthing
just remember do not abuse this kit, treat it well
many thanks