Hi, Fleur, welcome to the forums!
It's important to remember that some things matter for FICO scores, and other things matter to lenders. So if you want to go into the lending process with optimum scores, leave your CL's where they are. At that point, if they're twitchy about your limits, you can drop them then.
What many people do in this situation is let their card companies know that they need to temporarily drop the limits. Once the mortgage funds and is a done deal, they let their CCC's know, and their limits are restored.
* Credit is a wonderful servant, but a terrible master. * Who's the boss --you or your credit?
FICO's: EQ 781 - TU 793 - EX 779 (from PSECU) - Done credit hunting; having fun with credit gardening. - EQ 590 on 5/14/2007