There are 103 stations with no journeys to any London Terminal recorded. As well as the usual suspects such as Teeside Airport, Reddish South and Altnabreac, it also includes a lot of Glasgow suburban stations, which seems to be a bug in the data, as I find it hard to believe that of the 103k people who used e.g. Hillington West, not a single one of them was travelling to London.
There are 21 stations with just one journey to London recorded
Alness, Ardgay, Bank Hall, Barrhill, Braystones, Causeland, Cynghordy, Fearn, Golf Street, Hoscar, Kirkhill, Lairg, Llanbedr, Mosspark, Mount Vernon, Penychain, Pilning, Rannoch, St Budeaux Ferry Road, Thorntonhall, Thorpe Culvert.
The stations with more than 2000 different journeys made were
Manchester Piccadilly (2377), Birmingham New Street (2274), Leeds (2224), Manchester Victoria (2182), Liverpool Lime Street (2178), Edinburgh Waverley (2168), Liverpool Central (2151), York (2137), Newcastle (2125), Sheffield (2120), Manchester Oxford Road (2105), Bristol Temple Meads (2089), Nottingham (2079), Glasgow Central (2041), Birmingham Moor Street (2037), Oxford (2001)