Thanks guys for all your input.
OH and I visited our local Telefonica outlet earlier today, bought a payg SIM (9€) and a subscription to a tariff that gives access to the internet via 3G or our wifi router and unlimited Blackberry access. One free phone call to get the Blackberry Services activated, quick reboot and away she goes!
One minor snag is that with this tariff, emails are always routed from the Blackberry servers via Telefonicas 3G / 2G / EDGE network, but web access at home can be via our ADSL wifi router. Seems this is a little gotcha courtesy of Telefonica! (And various other service providers it seems). In the UK with Orange, the default was wifi for everything.
Our location in Spain only provides EDGE but it's better than nothing. Other service providers in our area require their customers to leave their homes and walk to the end of the road to get any kind of mobile reception!
Thanks again guys, your suggestions are most appreciated.
pp