My priority is to finish off the extended south-west and Wales, which includes most of the network west of Exeter, west of Shrewsbury, Hereford and Swansea to Shrewsbury some of the Valleys north of Cardiff, the Isle of Wight, Basingstoke to Fareham via Southampton Central, Salisbury to Exeter, Oxford to Worcester and the routes that cross the North Wales route at Llandudno Junction and Shotton. I also intend to complete the Underground - having now done the whole of the Met I can do that which remains on a basic 1-6 Travelcard in one day - and also London Midland and Chiltern, which means the Chase Line north of Walsall and the routes into Stratford-upon-Avon.
At a push, I would also like to say what is left of SWT after this, but that might be asking a bit much in terms of how much access I will have to the London area next year; I also need to do the Marlow and Henley branches (and also Heathrow), which would fit in well here. If everything was to go perfectly I would also add what is left of NXEA, which allowing for me hopefully doing the Braintree, Walton, Sudbury and Harwich branches later this month would in practice mean most of the West Anglia route (the Lea Valley, north of Seven Sisters and Clapton (except to Walthamstow) as far as Stansted Mountfichet, north of Cambridge to King's Lynn and Newmarket) and also Peterborough. At a push, I'd then like to add Cambridge to Hitchin, but that might be a step too far.