Best way to do Bristol - London Heathrow - Southampton - Bristol

Hello, I have to do a round trip with multiple stops. I wonder if anyone has some ticketing advice that won't break the bank?
Journey 1. Bristol Temple Meads to London Heathrow T5 (leaving 11ish mid-week, flight at 330pm).
Journey 2. London Heathrow to Southampton Central. (flight lands 1410). Overnight Southampton.
Journey 3 Southampton Central to Bristol Temple Meads (anytime from 1400).

I can see that Reading is the sort of possible route but is it possible to find a ticket that would allow me to return back to Bristol direct without having to go via Reading?

Possibly cheap advances Bristol to Heathrow via reading, Woking railair bus or Hayes and Harlington depending on availability and soton to Brizzle, plus a normal.single Heathrow to Southampton. Bristol to Heathrow returns are not valid via Southampton. If you have lots of time you could go out and back via Southampton with a Bristol Southampton and a Southampton Heathrow return, but unlikely to be worth it. You could also buy a return to somewhere like Brighton and add on Hayes and Harlington to Heathrow but again unlikely to be worth it unless no cheap advances as in the first example are available.

There's a bus from West Drayton to T5 that's usually more convenient than going via Hayes and Harlington.

Thank you for your suggestions.

Mims said:

I can see that Reading is the sort of possible route but is it possible to find a ticket that would allow me to return back to Bristol direct without having to go via Reading?

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Checking Bristol to Southampton, you can go via Reading or Salisbury. The via Salisbury ticket is cheaper, but the via Reading ticket just has a "not via London" restriction, so valid both routes. That would mean separate ticketing for the Reading to Heathrow journey and back and being able to break the outward journey at Reading.

MarlowDonkey said:

Checking Bristol to Southampton, you can go via Reading or Salisbury. The via Salisbury ticket is cheaper, but the via Reading ticket just has a "not via London" restriction, so valid both routes. That would mean separate ticketing for the Reading to Heathrow journey and back and being able to break the outward journey at Reading.

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Sorry, but unless the OP is making a very short trip from LHR, this won't work - an Anytime Return is only valid 5 days for the outward leg
There are fares to Heathrow routed Warminster-Salisbury which undercut the GWR ones considerably, however they do not appear to allow travel vua Southampton.