This is what I think could be realistic over the course of January and next summer (moreso next summer...) - just from hunches (Mirallas) and what it seems like the team needs (everything else).
Mirallas out - £20m
Gibson out - £1m
Howard out - £3m to MLS
TV Money - £30m
Deulofeu - £10m
Solid defensive CB, mid-late 20s (Reid or similar) - £10m
Pienaar type replacement, good vision, works with space, good passer - £10m (or perhaps Ayew on a free)
Mid-late 20s top-class goalkeeper - £10m
Lukaku installment - £8m*
Loss in prize money for finishing lower in the league - £4m*
Remaining £12m to be spent on a squad player or two to make up for loss of Gibson, Distin etc., or renewed contracts.
* denotes number pulled even further out of my arse than the others.