How to find the best-priced UK train ticket combos for not-quite-round trip journeys?

I do a lot of walking and hiking in the UK. Frequently, I need to find the best combination of tickets that will get me to the start of the walk and then bring me home. This is simple if the walk starts and ends on the same train line, but gets tricky otherwise.

For example, if I start at Vauxhall, and I wanted to walk from Salfords to Chilworth, I think it's Contactless from Vauxhall to Salfords, and a single Chilworth to Vauxhall.

If I wanted to walk from Chilworth to Brookwood, it seems like the cheapest combination would be a return ticket from Vauxhall to Chilworth and a single from Brookwood to Woking.

I found these by painstaking trial and error, and there must be a better way to search for these in general. Do any of the "split ticket" search engines have this as an option? If I instead of Chilworth to Brookwood, I wanted to walk all the way to Sunningdale, I don't think that Sunningdale to Weybridge would cover me for the return trip, but what would the best combination be, and how to find these in general?