I’ve purchased 2 pair of Takatsuki 300Bs from Parts Connexion with absolutely no complaints. Quick service, great packing, friendly staff. But, I’m in the States so cannot comment on tax/tariff to the UK.
Regarding the Takatsuki 300B, absolutely amazing tube. Slightly tighter bottom compared with Western Electrics, wonderful mids and sparkling highs, very comparable to the WE. Very thick glass envelope.
I received a pair of new production Western Electric 300Bs with 2020 date codes from Rossville (Georgia) Works. I’m just beginning to “age” them and so far am quite impressed.
And, if you are ever in Japan, Kyoto in particular, go visit Takatsuki. Appointments are made on their website. They are very friendly and proud of their operation. You can easily spend an afternoon in their listening room.