Hi André,
For Switzerland check out
Switzerland - Prepaid Wireless Internet Access.
"Sunrise Surf" (CHF 7.50/month for 250MB + CHF 0.10/MB for exceeding volume) will probably meet your requirements. The SIM costs CHF 19.90 including CHF 20.00 of credit. I've recently written a detailed article about it at
Switzerland - Sunrise - Prepaid Wireless Internet Access.
For four days in Germany I think Fonic with their daily flatrate for € 2.50/calendar day or their monthly flatrate (throttled after 200MB) for € 9.90/30 days could be interesting. Their SIM is sold for € 9.90 with at least € 6.75 of credit. Until July 4th it's even € 13.50 and you can get a bonus of another € 5 as described at:
Germany - Fonic - Prepaid Wireless Internet Access (see step 7 under "activation")
Regarding the UK, there's a recent thread on this board:
http://www.prepaidgsm.net/forum/euro...d-data-uk.html
Unfortunately there's no single product, that could provide reasonable data rates in all three countries.