British Airways Flying Club don't charge extra for IMC training - there's just one dual rate on the Warriors and Dakota regardless of what you are training for PPL, IMC or Night.
Sounds like another mark up scam to me, like the 'hidden' fuel surcharges, landing fees etc that some companies spring on the unsuspecting customer.....
BAFC Weather page is proving very useful:
http://www.bafc.co.uk/weather.shtml