Britain has 227 tanks in active service, and other tanks have been retired for storage. Bulgaria also has 250 reserve tanks. If you count these tanks, they will have 800 T72A/M2.
With all due respect, Bulgaria is the European country most capable of helping Ukraine, not Britain.
You should know that Bulgaria can mass produce T72. At present, Ukraine is most short of artillery and tanks, and Ukrainian soldiers can use T72 directly.
As for Britain, first of all, we will not talk about whether Ukrainian soldiers will use Challenger II. More than 200 British tanks are useless in front of 13000 Russian tanks, and the British production speed is too slow.
Only the Bulgarian T72 can really help Ukraine. Of course, the EU needs to pay Bulgarians.