1. They are not in London.
2. They believe you'll respond more favourably to an English name.
3. Tell them the next time that you don't have a Computer and that will put them off.
4. Register with the Telephone Preference Service
http://www.tpsonline.org.uk/tps/index.html
And this should help cut down on nuisance calls. If they are based in the UK (Once you've been with the TPS for a few weeks), mention the TPS and that they're breaking OFCOM rules. That'll give them something to think about.