Help! How should I investigate my dropped calls problem?

Time to tap the big brains of the readership this morning…

I’m experiencing a major problem with dropped calls at home.  Yesterday calls throughout the day dropped within a few minutes.  I suspect it may be a Three issue (the odd ‘network busy’ message), but it’s coincided with me starting to use new handset and I’ve been swapping phones and networks a lot over the last few months so don’t have a reliable benchmark point.

The techie in me feels I should be able to gather some firm evidence as to whether it’s the network or the phone beyond just testing alternatives to both for a while.  Is there any data I could get from my handset (or anywhere else for that matter) to give me a steer?