By returning in economy + the YQ is much less especially from UK
The premium cabin surcharge with UK origin flights is a separate APD tax, and not an airline imposed YQ surcharge. UK APD is currently $247.40 for both D1 and PS flights with a UK origin. UK APD on Main/C+ fares is currently $112.20, so the savings from lower APD are actually fairly modest at $135.20 (most of savings will be from overall lower fare cost). YQ on D1/biz fares is currently $955 each-way for TATL fares no matter what your origin airport is for US point-of-sale fares.