Catlovers

Hi everyone, We are building a brand new indoor boarding cattery, on the site of a former stable block. It's an L-shaped building, single storey, 140m2, with corridor down each side giving access to 12 cat rooms, a kitchen, and reception area. We've had quotes from 3 main contractors but they are all over our budget of £100k. They all seem to feel the cheapest way to build is timber frame constructed on site, tanalised timber cladding externally (like a shed / stable block) insulated profiled sheet metal roof, internal stud walls for cat room partitions, then insulation, plasterboard, 2mm upvc hygiene cladding (all cat room surfaces must be plastic clad for cleanability). Electric combi boiler (no gas here), wet underfloor heating, commercial vinyl flooring as used in hospitals. Non opening upvc windows, and a ventilation system. Building regs do apply because of the kitchen and reception area. We are stuck on alternatives to the main contractor build route. If we use subcontactors directly I am worried about making sure the design works so we have a functional building at the end (eg what if we end up with a condensation problem, or fiddly gaps filled with sealant that won't withstand regular steam cleaning?). I've got a quote from a stable manufacturer (they do barns, garages and garden offices too), for a barn style shell with timber cladding and metal roof, installed, for £30k, and a quote from a modular upvc cat pen supplier to fit out the inside with cat pens for £33k. But then I still need to have groundworks, external walls insulated, plasterboarded, hygiene panelled, electrics, plumbing and underfloor heating, ventilation system, external windows and doors, tarmac planings drive, etc. I just don't know where to start with finding tradespeople to do these things and making sure that they all work together so that the building functions well. The architect who drew our plans for planning permission is no help, he has never built a cattery before and has no idea what the requirements are. Anyone have any advice?