I drove back almost past the 'ring last year on my way back from my Europe trip, but I stopped off in Brussels so I'm not sure on the times. Bit longer than 4 hours I'd say. Most insurance includes cover in Europe these days, you just have to tell them when you're going. If you're in the AA, breakdown cover will cost you £34 for up to 24 days . RAC is much the same.
In theory if you are driving at night you should have headlight convertors, but I drove 3000miles and never bothered. Well actually I did buy some, but couldn't figure out where to stick them . Also in theory in Germany + Beligium you are supposed to carry a first aid kit, warning triangle and fire extinguisher. Oh, and whatever you do DO NOT take a radar detector or anything that looks like one into France. They will literally rip your car to bits to remove it and confiscate it. Driving over there is so much better than here though.
I just bought tunnel tickets to go to Le Mans this year - they were £113 return, but they were doing a special offer at the time which has now finished. If you join the points plus scheme you get 10% off (but it costs to join).