If more people understood about a trust for sale, Court probably wouldn't be necessary..... 

Likelyhood is that the OP and friend are already tenants in common seeing as they are not married nor cohabiting in the usual sense, so severing the tenancy really doesn't apply, whichever way round you get your terminology. 

And you can get mortgages on half shares.  Shared ownership schemes are increasingly common.  Even I  know that and I am no solicitor.

Cat