I'm putting some IP65 rated 12v downlighters into my bathroom ceiling. They're 50 watt bulbs around £6 each and I need 6. They come without a transformer so my question is, which transformer will I need? I have the choice of 60w or 105w - my guess is the 60w being as the lights themselves are only 50w but wanted to check with you experts(?) before I ordered...!