Peter wrote:

Isn't 3G (or any GSM-based data) going to be hugely expensive compared
to ADSL - even if you are not roaming?

Nope!

For a fairly low user, you'd pay £11 per month line rental plus £17 per
month ADSL charges

Using something like 3 Mobile Broadband on PAYG £10 per month is all
you'd have to pay. OK, if you exceed 1GB you need to pay another tenner
or pay a VAST per-MB fee, but most low users don';t gat anywhere near that.