Contractor Styles and Wood has taken a place on the four regional panels including Northern Ireland, and Shaylor taking the three mainland regions.
ISG, Havelock Europa and Interseve have also landed places in one region.
The firms will deliver the Post Office transformation programme which aims to revamp internal branch layouts, remove fortress counters and become more open plan.
The work also includes general redecoration including flooring, new shop fittings and internal signage, upgraded lighting in customer areas.
Under the four-year framework the firms will deliver part of a programme to invest in 292 Post Offices in cities and towns.
Royal Mail transformation works
Lot 1: Northern Ireland: Styles and Wood – £2m
Lot 2: North: Styles and Wood ; Shaylor Group; ISG – £6.9m
Lot 3: Midlands and South West: Styles and Wood; Shaylor Group; Havelock Europa – £6.9m
Lot 4: London and South East: Styles and Wood; Shaylor Group; Interserve Construction – £14.1m
