Circular route

[Halsebee]

Could anyone advise please?
I need to travel from Bath or Westbury or Frome to Weymouth late AM on a weekday this coming week, then from Weymouth to London mid PM, and return from London to Taunton late AM next day. What is the best combination of tickets to get the cheapest deal? Flexible tickets probably needed, although not absolutely necessary.
Can you for example get a ticket from somewhere between Castle Cary and Dorchester that is permitted route via either SWT or Berks and Hants routes, and buy a ticket from Bath to that station to cover the first leg, and a Castle Cary-Taunton single to cover the last bit?
Are there cleverer ways than that?
Thanks in advance

 

[yorkie]

A ticket from London to Maiden Newton is valid both routes, this is £55.70 SSR.

Taunton to Maiden Newton SVR is £16.30 but this is routed Not Bristol, so probably can't be justified from Bath, the excess on the outward to Route Bristol would be £5.45, but this probably isn't worth the hassle as a single from Bath to Westbury is £5.60. On the other hand, you could get a Bath to Maiden Newton single (£12.30) and a Castle Cary to Taunton single (£7.20) which is £2.40 cheaper.

BTW, a ticket from Maiden Newton to London is valid for doubling back within the Weymouth Group of stations, so there is no problem between Upwey & Weymouth on this ticket.