You'll notice that 77 is more than 70, so yes it is "fast" when compared to the speed limit. Also if the GPS in the black box clocked you at 77, then it's likely the speedo was showing 80+. Ultimately it's irrelevant whether you think it's fast or not, you've shown the insurer that you have little regard for the rules of the road, so it's no surprise they've decided you're a higher risk.
As far as servicing vs MOT, they are very different things.
The MOT is a check to make sure your vehicle is safe and roadworthy, and is a legal requirement.
A service is regular maintenance, e.g. changing the oil, filters etc., and while there is technically no requirement to have one done (at least not on a 13 year old car which is well out of warranty), it's definitely advisable if you want to keep the car actually running (not to mention you are legally required to keep it in a roadworthy condition).
On such an old car though, I'd definitely suggest learning how to to DIY it. On most older cars it's a pretty easy job with plenty of youtube videos to show you the steps, and requires only a few basic tools.