We're starting to plan a driving trip in England this summer. Is Google Maps pretty accurate for timing & directions--or is there a more reliable site? (We had a terrible time with Google maps in Seattle, but elsewhere it's been very good for us.)
It's as good as any other software/gps. Or as bad.
Directions will be better than time. Time can be off in either direction since it's computed by posted speed limits and assumes you'll be right at them instead of caught in a snarl or moving along at the limit plus ten.
If you need to pre-plan anything close enough that the differences matter, you're doing something wrong.
You could also look at ViaMichelin. I usually check both. Remember to leave time for picture taking. I find that I need to add 25% to any time in Via Michelin.
Some of the rentals come with their own navigation. My backup plan is an "old school" paper folding map or book: that way you can sit on the bed the night before and circle your next day destinations and sites on the way. I think the UK AA may still have these with one inch equals one mile; excellent for finding the way to that farmhouse b & b.
Also, if you don't use a GPS you really should plan your route before you leave. I travel solo, so I always make a list of the major towns and cities on my route. The reason is that sometime the easiest signage to read are those that point you to the next town. The UK roads are less likely to have sign that says: A9 North. It is more likely to say A9 Perth or A9 Inverness or A9 Golspie depending on how far north you are. :) Sometimes it won't even say the A9. It will just say Perth.
I think that this applies in Europe in general, but I've driven fewer miles there. I did once drive from Chartre to the north of Paris, but following signs with city directions. The TI told me that was the best way!