Random GMail delays AGAIN :-((

I have a number of accounts (Google Apps for My Domain) integrated with a BIS (on T-Mobile UK). These are all fully integrated accounts (NOT set up manually/IMAP). Email is normally instant, but can be delayed a hour or more after it can be seen on GMail's web interface.

This is perhaps during busier periods for RIM's infrastucture. Certainly it normally good during the UK morning (small hours in the US). And when it's bad I get "clumping" of emails - delayed mails arrive in a bunch.

It's almost as if when things get busy the Google service degrades to a polling rather than fully push algorithm.

I have tried deleting and recreating some of my email accounts on the BIS. It hasn't helped. I now have a small message base size on my BB, and reduced the total number of mails in my Gmail accounts to (each) below 5000 and 300MB. There's nothing in my inboxes (I archive everything as soon as I read it).

Anyone else see this and/or suggest a fix?