wow, lorra money for WT+.

Depends how much you value your comfort, I've done WT+ LHR-SYD-LHR and it's fine, leg room is excellent and the extra seat width makes a difference. It is a whole lot better then being in the zoo, but I have never done a trip that distance in the back.

Mrs PG and I went GF business class LHR-SYD-LHR for about £3.2k earlier this year, slightly longer flight as you stop in BAH & SIN both ways. This played about £3k for WT+.

Bearing in mind you have got two nights on the flight, I would lean towards WT+, but it really depends how much the £2k means to you. I'm 6ft 2in, so leg room is a must.