Not themed, as such, but I've always intended taking (but not yet done so) the Watercress Line from Alton to New Alresford, then bussing it down to Cheriton. From there, you could re-trace your route or take bus to Winchester then, if staying over, go on to Southampton.

Alton: Railway Arms, Eight Bells, bus to Selborne (~14mins)
Selborne: Selborne Arms, rtn bus to Alton, Watercress line to New Alresford
Alresford: Maybe The Bell?, Option of The Ship (Bishops Sutton, 1.3m), bus to Cheriton
Cheriton: Flowerpots Inn, Hinton Arms, bus to Winchester
Winchester: (from memory) Black Boy, St James' Tavern, Hyde Tavern, maybe Fulflood & Wykeham Arms, train to S'ton
Southampton: Wellington Arms, Guide Dog, Waterloo Arms, Red Lion, maybe Duke of Wellington, South Western (next to St Denys station), transport to... Betty Ford clinic