Greetings NYM! I'm not exactly sure just where the alligators might be based, but depending on your wherabouts, you might be better off with more localized railrovers, the details of which can be found in great detail here:-
http://www.nationalrail.co.uk/times_...nd_rovers.html
As for loco-hauled services, they're a bit thin on the ground nowadays, more's the pity. Basically, the London Liverpool Street to Norwich services are mostly hauled by Class 86/2 electrics, a couple of Birmingham/Euston services are sometimes Class 90 hauled, some services to/from Paignton/Taunton to/from Cardiff may be hauled by either Class 57/3 or Class 67 (usually one at each end), one train in each direction most days between Cardiff and Holyhead via Crewe are Class 57/3 hauled, overnight Penzance/Paddington sleepers are hauled by Class 57/6, and Euston/Scotland sleepers are Class 90 hauled. There's a new commuter working just started up between Carlisle and Sellafield using DRS 47s, but that's ludicrously early from Carlisle. A few workings in Scotland are hauled by Class 67, and that's about it - other than Specials & charters. There are some Glasgow/Southampton services operated by Class 47s (mostly), but these are in conjunction with cruise ships, and not the sort of train a chap can just jump on!
Good luck, and let us all know how you get on!
