Frame upgrade help

My brother is a MTB fanatic and a few months ago gave me a titanium frame. It needed the brake bridge to be moved 1" to work with 700c wheels which has been done. As part of my work I work with the welding institute so it is a very good modification.

I'd quite like to sell it now it's fixed and buy a new frame for my size. How much can I expect to get for it? As this will be the majority of my new frame fund.