Sorry, forgot to update - I've cracked it! Nokia Maps was only accessing the area over my WLAN connection, or trying to use GPRS for localised mapping. I had loaded Nokia Map Downloader, but tried to download the whole of Europe, rather than just one country, hence 1.4GB download and the phone crashing. Managed to reinstall, load JUST England, and it works brilliantly, e.g. I was in Birmingham the other day, used 'Find place > GPS' to locate, then zoomed in and behold! details of train stations, bars, restaurants, including phone numbers, right off the memory card, no 118-118 rubbish.
Pete