i am not quite sure that Truphone will lower their rates... even with today's market standards, their rates are higher than competition. i wouldn't recommend them.
have a look at maxroam simcard, they now offer a true UK number (Vodafone).
http://www.maxroam.com/Info/Custom/M...3.aspx?cur=EUR
their roaming rates can be found here:
http://www.maxroam.com/Info/Rates.aspx?cur=EUR
you can also attach on your sim a US number..costs 6eur.per month with no extra charges when be called on the US number
another good alternative with a true UK number prefix (not IOM or Jersey numbers) would be piranha mobile
http://www.piranha-mobile.com/ .their prefix is +4474185 plus they offer a US number for free, automatically attached to the simcard.
you can also attch local landline numbes for almost all countries for just 4pounds per month, with no extra charges when be called to these numbers.
local uk+german landline numbers cost just 1.75 uk-pounds /month