If you want to sell it in the UK, post it in the for sale section here:
http://www.brass-forum.co.uk
There are some other links to other band pages that might also help you sell it.
VMI model 103 Tuba for Sale in UK
Forum rules
This forum is for buying or selling your personal equipment. Sponsored selling is allowed as well. All ads are required to have the following information: Price (even for trades), brand, model, and location (City and State, for instruments, not accessories). It is acceptable to link to an external ad if you are promoting a sale of your personal equipment. No Ebay auctions, but "Buy It Now" listings are fine. Photos are HIGHLY suggested as well, and may be hosted on Google Drive, or elsewhere. If you see an ad that does not meet these criteria, please report it.
This forum is for buying or selling your personal equipment. Sponsored selling is allowed as well. All ads are required to have the following information: Price (even for trades), brand, model, and location (City and State, for instruments, not accessories). It is acceptable to link to an external ad if you are promoting a sale of your personal equipment. No Ebay auctions, but "Buy It Now" listings are fine. Photos are HIGHLY suggested as well, and may be hosted on Google Drive, or elsewhere. If you see an ad that does not meet these criteria, please report it.