hi Peter and thanks for reposting.
personaly my merchant sells 'Bristan' bar mixer to replace that. its all brass and made in Buxton.
That gives easy access to all parts when required and they even 'sometimes' send them free.
They also only cost about £50-70 which is rather cheap for a top brand compared to the high priced tat they sell in sheds.
unfortunatly, i cannot give you a ref number for the item, but if you go to a decent merchant i'm sure they will have some.
update: this is a very good price- https://www.argos.co.uk/product/6225391
not sure if its the same model but looks simular- easy fir and 5 year warranty cant go wrong!