I feel your pain. I still have £400 on the credit card from January. Had 4x Michelin PS5s fitted, but got £70 off and a £50 Amazon voucher.
This was at ATS (owned by Michelin). Normally I hate chains, but amazingly the slow loss of air I used to get on the rear left has been solved. I've been living with it for 5 years and had umpteen places refit various tyres on that corner with no success. ATS seem to use proper white tyre paste which has finally sealed it (took a lot of scrubbing to get it off the alloys).
Michelin Tigre is the stuff going off a Google search.