This has been posted previously, and the population figures were from 2013, so may have changed a bit since then. This list only applies to England:
Towns without stations.
The "official" definitions of towns & their boundaries have changed over the years, especially in the 1974 reorganisation (Whitehall meddling) in which various towns & villages were lumped together into metropolitan boroughs or other units deemed an "ideal" size by Whitehall. For example, Hanley is a fairly large town with no station, but I could not locate a recent population separate from the combined "City of Stoke On Trent".
Also, information on Wikipedia is not always reliable. The following is an attempt to determine the population of towns, according to "traditional" boundaries, which have no station in or near the "town centre". Separate lists show towns with stations near the edge of the town, and towns with trams but no "mainline" railway station. Populations rounded to the nearest "thousand".
1. No station:-
Wythenshawe 86,000 (Technically part of Manchester, so should be deleted)
Gosport 80,000
Washington (Co. Durham) 53,000
Middleton (Lancs.) 45,000
Leigh (Lancs.) 44,000
West Bridgford 44,000
Skelmersdale 39,000
Ilkeston 37,000
Blyth (Northumberland) 36,000
Houghton le Spring 36,000
Dunstable 35,000
Coalville 33,000
Peterlee 30,000
Rushden 29,000
Heywood 28,000
Ashington 27,000
Consett 27,000
Haverhill 27,000
Burntwood (Staffs) 26,000
Daventry 25,000
Newport (I.O.W.) 24,000
Kenilworth 23,000
Heanor, Clevedon, Portishead all 22,000
Ripley 21,000
Hailsham 20,000
2. Only station is on fringe of town:-
Dudley 195,000
Halesowen 55,000
3. Towns with trams but no mainline rail station:-
West Bromwich 137,000
Oldham 103,000
South Shields 82,000
Gateshead 78,000
Bury 60,000
Wallsend 42,000
North Shields 40,000
Whitley Bay 36,000
Jarrow 27,000
Fleetwood 26,000