For Europe and specifically if you need European ccTLD's, inwx.de and netim.com have the largest selection and good prices.
You can see other European registrars on this page but check if they support all the TLDs you need and the pricing, sometimes they have an oddly expensive price for one of them.
Oh and a note about Gandi because it's listed as "cheap" there, they're currently jacking up their domain prices across the board. Until now they used to be sort of expensive, after this they'll be the most expensive by 75-100% than the others.
I renewed one of my domains in a panic because auto renew somehow turned off and yeah....wish I didn't panic because Gandi is expensive as hell now. Guess I'll move everything in a year
Remember that some TLDs will retain their validity period when transferred, so you can transfer them ahead of time if needed.
Look it up on the INWX TLD list and click on the ones you're interested in. They have very good information about each TLD. You can find out if the leftover term transfers over, how long the transfer can take, if there's a transfer fee (and whether it translates directly to the renewal cost) etc.