😊 update. After several more futile attempts I’ve got the new tyre in place! I soaped the beads and installed the tyre with a tube. I pumped it to 100psi and it seated nicely on the rim. I left it for three days to stretch the beads. Today I placed the wheel horizontally over a bucket to avoid compression of the tyre and deflated the tube. I then opened one bead, removed the tube and added the tubeless valve. Then I carefully put the bead back in place trying to avoid pushing the other side into the well. Finally cranked up the Topeak booster and gave it a blast at 160psi, rather than air rushing out, it popped into place and sealed. I then removed valve core, added sealant and pumped back up to 70 psi and went for a test ride. All good. So a right palaver but have learned a lot about tubeless. I probably wouldn’t start this journey again but will enjoy the ride for the lifetime of these tyres at least.