What level of delay am I putting in for delay repay and do I need to do 2 claims?

I'm hoping for someone more knowledgeable on ticketing to help me out here.

I had bought in advance an anytime single to Clapham junction not via London termini

I turn up and find my train will be running fast into Waterloo as it's delayed and is no longer calling at Clapham.

I then get an overdistance ticket to Clapham junction must go via London termini.

I then only use my overdistance ticket into Waterloo but not back to Clapham junction. (And the train arrives into London Waterloo delayed)

The options I see:
A) claim the whole lot as the difference between my original planned arrival time and the time I would have got to Clapham if I'd finished my journey using my overdistance (36 minute delay)

B) Claim the not via London termini ticket as the delay if I'd gone not via London termini (39 minute delay) and then the must go via London termini ticket as the delay going via Waterloo to Clapham (18 minute delay)

C) claim the not via London termini as in B) and the must go via London Termini as my delay into London Waterloo as I didn't actually go to Clapham (18 minute delay)

You didn't go to Clapham, and that is the only thing that actually happened, so C.

The unused ticket can be refunded from the retailer.

Is the overdistance ticket you got an excess or a seperate ticket?

It's an excess I believe (a lot cheaper than a standard ticket and says must be used in conjunction with my original ticket)

If it's an excess and not a new ticket you need to claim for both the original and the excess as one ticket as per C, no retailer refund due on the original as it has been used.

Thanks. I'll try and get this through the system