No. Only the Proprietor(s) registered at the Land Registry can borrow against the security of land. The simplest way is to change the Register to joint names before approaching a lender, and if you wish to do this yourself phone your District Land Registry Office who will guide you through the small number of (easy) forms involved, the Land Registry Fee and the declaration to the Revenue. Otherwise it is a solicitor at a cost of about �250.
Not as such. Only the ownere of land can grant a mortgage over it. Your partner could obtain a mortgage, or could put the land into your joint names to get a joint mortgage.