In reply to whenry:
If you want a one-off complete solution that you can use across 4 devices (phone, PC, tablet), buy Memory Map for the UK at 1:25,000 and install the whole map (~25-30GB) on a microsd card on your phone (bit trickier if you have Apple with limited storage).
Job done. Don't have to rely on download/subscription. I use it near enough every day on the PC as well.
But full price is £275. But they usually have half price/big-discount sales later it the year.
Note - there can be some faffing/geeking to get the big file on phone and working right, and you might need access to PC. We also had issue on one of our phones where a new 128GB SD card (formatted correctly) wouldn't work right with the file, but the older 64 GB card would.
Post edited at 09:16