[Stuart]

I assume Carlton saved money by outbidding them for the London Weekday ITV franchise instead of buying them directly?

I think at that time Carlton just wanted to be a 'publisher broadcaster', commissioning programmes instead of making them, rather like C4.  It was only when they bought Central that they became more involved in production.

I'm surprised that they seriously considered buying Thames in 1985, who were quite a prolific production house.