The Swiss WTP fare can be 277CHF cheaper for 40k Avios. Assuming you'll earning 50k-ish on the 3x Promo, I'm thinking of throwing a Joker and a GUF at it to make the total cost around £250 return, I'll be in CE/CW and when the miles post I'll be 10k-ish Avios better off, plus 210 TPs.
Unless my maths is off?