The dilemma is that, as has been pointed out, there would be completion issues in many areas with the 'big five' buying bits of First UK Bus. Equally, the economic state of much of the industry at present will probably mean most of the groups have little enthusiasm for buying further problems, unless there are particular strategic or good 'fits' (though of course these are the most likely to give rise to competition concerns).
The independent sector in many cases has neither the cash nor expertise to take on a chunk of First, and the 'medium size' groups and those independents with capability would only be able to cope with a very limited level of acquisition - both in terms of affordability and the management resource to sort out the problems. Whether these problems are caused by local economic conditions, or historic bad management in the Blockhead era, they take a very long time to sort out. Passengers who have deserted do not return quickly, whatever a new owner might do.
And of course in some of the PTE areas, the threat of franchising means the number of likely buyers will be at best very limited - anyone who does so will effectively value the business as assets (at best).
Add to this the inherited working practices, wage rates, pension liabilities (which may or may not be transferred) etc and in many cases it would be better to start with a clean sheet.
In summary, I think the outlook for First UK bus is largely (at best) sales at or around NAV, or in other instances, closure. A sad state of affairs.