Last time (about 3 years ago) we purchased a separate rental car insurance policy from a third-party company that specializes in such. Can't remember the name, sorry, but I'll keep looking. Meanwhile do some Googling on "rental car insurance policy UK" and see what you find. We were there a month, and it was WAY less expensive than insuring through the rental company. If you're putting the car on a premium credit card, that also insures you to a certain extent (check w/ your credit card co. to be sure) but we went with the extra coverage to be on the safe side.

IIRC it's actually a 6-mo or year-long policy that covers any car you rent during that time.

FYI, if you are left-handed, you will likely adapt very easily (according to two sisters and mother who are all lefties and have driven there).