But how have the rest of League One been faring in these financially difficult times?
Here we list the arrivals and departures of the clubs who will try and stop Posh winning an immediate return to the Championship. We also rate their transfer business out of 10.
All transfers logged by the BBC from the end of last season and up to and including June 30.
Departures listed are those who have found new clubs.
1. ACCRINGTON STANLEY
Ins: Matt Lowe (Brackley), Lukas Jensen (Burnley), Mo Sangere (Newcastle). Outs: Matt Butcher (Plymouth), Ross Sykes (Union SG, pictured right). Summary: The two departures are a loss, but this club defy a tiny budget every season so don't write them off. Transfer business rating: 4/10. Photo: Joe Dent
2. BARNSLEY
Ins: Jamie Searle (Swansea), Luca Connell (Celtic), Robbie Cundy (Bristol City, pictured right), Conor McCarthy (St Mirren). Outs: Patrick Scmidt (Admira Wacker), George Miller (Doncaster), Cauley Woodrow (Luton). Summary: Woodrow would have scored goals for fun in League One. Posh look in better shape than a team that came down with them.
Transfer business rating: 4/10 Photo: Joe Dent
3. BOLTON WANDERERS
Ins: Jack Iredale (Cambridge), James Trafford (Man City, pictured), Connor Bradley (Liverpool). Outs: Liam Gordon (Walsall). Summary: Keeping hold of Manchester City goalkeeper Trafford for another season is huge. Big club who will be all the better after a first season back in League One. Transfer business rating: 6/10. (Photo by Gareth Copley/Getty Images). Photo: Gareth Copley
4. BRISTOL ROVERS
Ins: Jordan Rossiter (Fleetwood, pictured right), James Gibbons (Port Vale), James Connolly (Cardiff). Outs: Sam Nicholson (Colarado Rapids), Cian Harris (Swindon), Jon Nolan (Tranmere). Summary: A less than inspiring transfer window so far. Transfer business rating: 4/10. (Photo by Pete Norton/Getty Images). Photo: Pete Norton