Just 16 records in the UK up to 8-June-2022, majority from Wilts & Somerset, so hardly evasive? Known as a Peking Robin in the caged bird trade and banned as a UK import in 2005, and no longer abundant as a captive bird (info from BBC discoverwildlife.com)
For myself, many years ago, I once saw a small party of 6 Zebra finches in my garden in Middlesex, and found a male Red-cheeked Cordon-bleu feeding with a small party of Dunnocks at Billing Aquadrome in Northants, all undoubtedly escapes.

It’s not exactly much of a cluster yet, but a few records around Frome / Warminster. BTO do ask that you record it on Birdtrack (or iRecord):
https://www.researchgate.net/figure/Records-of-10-Red-billed-Leiothrix-sightings-black-symbols-in-the-Wiltshire-Somerset_fig2_361109680

Just had one in the garden in Shapwick apparently they are on the increase in the uk, with there being a group of sightings in Somerset and Wiltshire
Gave me a hell of a shock , just for a second I was racing to get my Sibley and claiming something Yank and stupifyingly rare.