SQL hosting

I've seen lots of people advertising SQL server hosting for web-fronted
apps but we have 25 sites using a proprietary front end developed for us
in (? dunno yet) with a SQL server back end.

We have 250 employees across all sites with maybe 25% of these actively
using the system at any one time, but apart from bursts of reporting
action the actual database use is not heavy - booking appointments and
checking customer records - some of the smaller sites may process fewer
than 10 records a day. With the amount of historic data we have to keep
I estimate we have about 50GB data across all databases.

At the mo we have the offices using their own SQL server or MSDE for
some of the sites with a bit of replication between some of the servers,
but it would seem that an ideal solution would be one (or two for
redundancy?) central (but very reliable!) server(s) for the whole
operation with the sites using WAN/VPN links to access the central
server. From my perspective this would give us more control over data
management and backup, and fewer individual servers to worry about.

At the mo, the developers have no plans for a Web-based front end but
this may change with customer pressure.

So folks.. the questions for today are...

1) How practical is this solution (ie: centralised SQL with non-Web clients)
2) How does one maintain reliable links to the sites (BB with ISDN
backup over different circuits, GPRS!...?)
3) Who's worth talking to about this?

Thanks

L3K