The first question on any Hinckley loft is head height, and on the late Victorian housing near the centre the answer is often better than people expect, because those roofs were built with reasonable pitch.
Measure before you get attached to the idea though. A roof can look generous from the hatch and still leave you short of two metres along the walking line once the floor build up and the insulation are in. We measure at the quotation rather than after.
The permitted development volume allowance is forty cubic metres on a terrace and fifty on a semi or a detached house, which sounds ample until a dormer is drawn and it is not. A dormer on the roof slope facing the road is not permitted development anywhere, and in the Druid Street conservation area, where the buildings read as a single tightly dated group, anything that changes the roofline the street can see will be looked at hard. Rear dormers and rooflights are a far easier conversation.
The modern estate housing out towards Burbage and Barwell is trussed, which means the structure has to be reworked rather than simply strengthened. That is normal work and we do it regularly, but a trussed roof and a cut roof are not the same job and should not carry the same price.
Escape, fire separation and stair position are all Building Regulations matters and all easier to solve on paper than after the joists are down. Our loft conversion page goes through the structural options.