Book UK trains early — the discount really is that steep
Advance single tickets on UK intercity routes can cost a third of an on-the-day walk-up fare, but the cheapest tickets sell out first, not last. Booking 8-12 weeks ahead for a Friday evening or Saturday-morning departure typically finds the best prices; booking a week out on a popular route often means paying two or three times more for the exact same seat.
Weekday versus weekend pricing
Hotel rates in London swing the opposite way to trains — weekday nights are usually the most expensive (business travel), while Friday and Saturday nights are comparatively cheaper. In Bath and Edinburgh it's the reverse: weekend nights are the busiest and priciest, and a weekday-adjacent trip (Thursday-to-Sunday rather than Friday-to-Sunday) can meaningfully cut the total cost.
A realistic budget, per person, per night
Budget roughly £120-£220 a night for a comfortable mid-range hotel in any of the three cities, plus £40-£70 a day for food if you're eating well rather than minimally. London sits at the top of that range more often than Bath or Edinburgh, but the gap is smaller than most people assume once a specific hotel and a specific weekend are actually compared.
Luggage and pace
All three cities are walkable enough that a single carry-on-sized bag makes the whole weekend easier — Edinburgh's Old Town in particular has cobbled streets and slopes that are genuinely unpleasant with a large wheeled case. Reserve a seat with luggage space on any train journey over about two hours; UK intercity trains have limited dedicated storage and it fills up fast on Friday-evening departures.
Regional differences worth knowing before you go
Scotland issues its own banknotes (Bank of Scotland, Royal Bank of Scotland, Clydesdale) alongside standard Bank of England notes — both are legal currency in Edinburgh, though some shops outside Scotland are unfamiliar with Scottish notes if you bring cash home. Tipping in all three cities is optional rather than expected: 10-12.5% for a sit-down meal if you were happy with the service, nothing obligatory for cafés, pubs or taxis.