Post Office Insurance is worth a try.
On a couple of occasions I've spent several days trying to find a better deal than the renewal price that I've been offered by Post Office Insurance but I've always ended up finding that they've already found the absolute lowest price available. Further, whenever I've needed to phone them, I've always got through straight away and found their staff to be knowledgeable and helpful.
Post Office Insurance is on 0330 018 3770 (0800-2200 weekdays, 0800-1800 Sat, 1000-1600 Sun).
I've never found getting an MOT to be a problem (except when it's turned out that my car is beyond economic repair). I just leave my car outside the local garage one evening (dropping the key through the letterbox) and walk back down there at teatime on the following day. The mechanic will have checked over the car, repaired any faults, taken it up the road for a test and brought it back again, usually for a remarkably low price.
I never even think about vehicle tax. I pay by direct debit, so it just comes out of my account automatically every month.
Servicing? Er, what's that? If it ain't broke I don't fix it ;-)
(OK, I might possibly get the oil and filters changed at the same time that the car's in for an MOT but that's about it).