60k - 80k Decision! Can it be done?

[ThomasJr]

I find myself in a scenario where I have a 3 story building (estimate 160sqm) in need of a major renovation in the North west of England.

Intentions are to convert the building into a 4 bed 2 En suite 2 off suite Home, average finish, fully project mange the build myself Subcontract Etc. 

Starting with Inside
• A complete strip out
• Structural Tie rods to Tie the building together, I believe 
• Roof only 1 of 2 Upsides, it needs some strengthening with new timber 80% good repair 
• Complete wiring + storage heaters 
• Plumb the showers, sinks, sewers no central heating
• Windows the other Upside, are brand new both front & back
• Slab + plaster 
Outside
• Guttering 
• 30 % plastering example around reveals + soft spots

Important points Building is not Listed the ground floor is commercial so (Change of use planning) I have not had a survey done yet still I witnessed the work done on the previous neighbors same building however they are no longer around to seek advice. 

My questions are,
1. How do I establish an estimate i.e. building cost per square meter?
2. Where would you suggest I could keep costs down?

Finally time isn’t entirely priority but within reason.

Thank you for viewing.