The best way to have a good idea is to have lots of ideas.
The Two Body Problem refers to the difficulty academic couples have finding a job at the same university or at two universities within communing distance such that they can live together while perusing their individual careers. This is a problem that has been playing on my mind recently, and I had assumed that the only solution would be to live and work in London.
To test this I used the excellent Mapumental website to find overlapping communing areas by public transport. Assuming an arrival time of 9:00 AM and maximum commute of 90 minutes it was possible to produce commuting maps for up to three locations at a time. I used the main post code of each the Russell Group Universities, so the results may differ for universities with multiple campuses.
Below I have listed the overlapping commuting areas. The lighter the area on the map the more universities are in range.
It is possible to live in either Edinburgh or Glasgow and commute in under 90 minutes, a number of small towns (Falkirk, Linlithgow, Bathgate) are within an hour.
While Newcastle and Durham are and obvious pair, and you can live in either and commute to the other in less than an hour. It is also worth noting that you can get to York in under 90 minutes.
Indeed Central York, Central Newcastle, Central Durham, Darlington, Chester-le-Street, and a few smaller places are within 90 minute of these three universities.
North West/ Yorkshire/ North Midlands
The denser clustering of Universities in the North West provides more options.
Liverpool Manchester is another obvious pairing, and large areas of both cities are within a 90 minute commute of both cities, a few mid-towns such as Warrington are within an hour of both Universities.
Manchester also shares a commuting area with Leeds. Central Leeds, Central Manchester Huddersfield, Hebden Bridge, Halifax, and Stalybridge are all within 90 minute of both Manchester and Leeds Universities.
The centre of Leeds turns out to be a good place to be, as it is also within 90 minute of Sheffield and York Universities. Much of Wakefield and Doncaster is also in the 90 minute zone.
Central Manchester is within 90 minute of Sheffield Uni, but not vice versa. A large area of Stockport and a number of smaller areas are within 90 minutes of both Universities.
Central Sheffield is also within 90 minute of Nottingham University, as is Mansfield, and Chesterfield. Central Derby is within 60 minute of both Nottingham and Sheffield Universities.
Another obvious paring is Birmingham and Warwick Universities, but Burton-on-Trent and Tamworth link in Nottingham. Central Birmingham, East Birmingham, and Coventry are within 60 minutes of Birmingham and Warwick Universities.
The Centre of Birmingham, Warwick, and Leamington Spa are all within 90 minutes of Oxford University.
South / Wales
Reading and Basingstoke link Oxford, Southampton and London Universities
Central Swindon links Bristol and Oxford
Bristol and Cardiff is another obvious pair
Exeter and Bristol are just linked by Taunton
Bristol and Birmingham are linked by Cheltenham and Gloucester.
Poor Cambridge is only connected to London with a string of middle-towns.
Three of the London Universities for completeness
In summary there are more options than I expected several places provide access to three universities although London is still but far the best connected location.