I think GNE should invest in new buses for:

WheyAye50 Service 50 which operates from Durham to South Shields via Chester le Street and Washington.

Fab Fifty Six Service 56 Sunderland to Newcastle via Concord and Gateshead.

The Reasons I'd buy new buses for these services are quite simple.
1.) Both services suffer from Capacity Issues, Morely 56 at Peak Times.

2.) The Buses on the 50 are pretty much knackered beyond repair, and they are always braking down somewhere between Chester le Street and Washington. and there always another branded bus on this service e.g. Lime/Lambton Worm or a Northern Decker.

Evidence http://www.flickr.com/photos/adammalarke...otostream/
This was at Lambton yesterday morning (Broken Gearbox)

3.) The buses on the 50 have suffered to Very long journeys in there 13 years with GNE, Notably on 50/57 and the 527/557 when they were first bought.

There is other service that could do with new buses including the Lime 8/78, but I think the 50/56 are more important. Even if the 50/56 did get new buses in 2013. the buses off the 56 could then go on the 8/78 which result in an improvement of better and recently refurbished Wright Solars for the Service.

The other services would be the 28/28A and the 34/34A which use old DAF Plaxton Prestiges, but knowing what GNE are like this probably won't happen for a while yet.

Thats if they are successful with there bid of course.