In reply to MGA:
http://xn--iphignie-f1a.com/ is an excellent app. All of france at 1:25000 - app costs about 4 quid and you need to get the annual subscription (10 quid) if you want offline maps. Note that you must get the annual subscription not the monthly one, as if the monthly one doesn't include downloadable maps and you can't upgrade to the annual subscription until after your month is up (if you do by accident, email the developers who will sort). Really good.
(The app isn't in french btw)