The problem in answering this question is that every hotel is free to set its own rules. However, if you've booked a hotel or package deal with Thomson, any requirements such as this should be in their brochure (or on their website).
I actually doubt that you'd need a credit card in almost any hotel within the EU. A lot of US hotels seem to operate this policy (even on package deals) but it's far less common in Europe.
To be certain, contact Thomson on 0844 871 0879 (Weekdays 09:30 - 19:30, Saturday 09:00 - 16:00, Sunday 10:00 - 16:00).
If you're looking for a first credit card, try Capital One. They hardly ever turn anyone down. (The interest rate is horrendous but you won't pay interest anyway if you pay the balance off each month. That way you can build up a good credit record and apply elsewhere for a card with a better rate at a later date):
http://tinyurl.com/cap1card
Chris