building regulations and mortgages

jo_t_2

We are looking at buying a period property which has recently been converted from one detached to two semi-detached houses. All building regs have been complied with except those concerning thermal insulation and double glazing. The vendors have left all original windows intact (apart from sympathetic restoration) and have declined to insulate the interior of the solid walls as per building regs requirements. Complying would destroy beautiful original mouldings, cornicing and plaster skirtings, antique glass and sash windows. All other building regs regarding structure and safety are complied with. If we accept the lower insulation values will this affect getting a mortgage on the property? The building has many beautiful original features and is in a conservation area, but is not listed. If it does not pass building regs in this one aspect will it make it un-mortgageable? Are there any ways round this?