Another trip to DLC, this time I decided to use ex-EU which gave me WT+ for half the price from LHR.

I now know the trick that WT+ on BA is only is only a small premium if combined with economy on the other flights, but it is impossible to book online, and the only way to get a quote for mixed classes is to use ITA and qualify the BA flights with /F BC=T

Turns out that Trailfinders don't charge a fee for booking BA flights as BA gives them a commission for flights out of UK, but ex-EU Trailfinders wanted a £50 service charge. Fortunately this time BA could see the fare (and there was no telephone booking fee).