A top tip, if I may suggest same; The old GBTT's are available to purchase on a download basis at 10 nuggets (£) each, from
https://timetableworld.com.
I have a run of same for the years I was travelling around, and in the here and now they have proved invaluable in my efforts to retrace my old trips I made back in the 70/80's, allowing me to put together many itineraries that I have long since lost many of my original notes of. That in itself brings back memories of those times, which I can't put a price on, so to those at 'Timetableworld' a massive thank you from me, having chucked my original GBTT's in the bin each year after they became out of date, as many others will also have done no doubt!