Property Loan 20 - Repaid in full after Default

Not something that's likely to happen, it's just discussing very unlikely eventualities and where people might stand if those unlikely things were to happen. Personally I'm confident that that sort of thing won't end up happening even if in extremis it's what could happen.
Were any of those loans taken out by FC itself? For this loan, Lendy is the borrower from the consumer lenders and has the obligations to pay. It's expected that the ultimate borrowers might not pay but it's not expected as a routine event that a P2P platform will take out a loan and not pay. One of the selling points of these older loans is that Lendy had that payment obligation so things like it not being necessary to worry about which loan money was lent on happened as a result.

The more recent loans at SavingStream aren't directly to Lendy so that issue doesn't arise for them. And for new loans taken out from 11 May it's also clear that there is no obligation to pay interest until after sale of assets if the ultimate borrower defaults.

Of course in this case I think that Lendy will ultimately pay.

There's legislation relating to Unfair Terms in Consumer Contracts Regulations and guidance from the OFT on it (now CMA but the guidance bears the OFT name). For Lendy to argue that it is not responsible for repaying money that it borrowed in its own name, as it did for this loan, would be a good example of such an unfair term. For new contracts since 2015 the unfair terms in consumer contracts law has been replaced by the Consumer Rights Act (2015) and the CMA has a guidance document on what the rights are.

Both an unfair contract term and breach of FCA guidance on what it expects in contracts between consumers and financial businesses that it regulates. Such a term needs to specify the circumstances and possible natures of the changes. This is one reason why most people who have bank accounts over the last few years have been getting notices fo variations in terms that adds details of when the terms might be changed instead of a whenever we like version. A firm can't just go and disclaim all of its past statements about how it would act, except possibly for new transactions carried out after the change, and even then if there is not a specific revocation of an undertaking I'd expect it to still be bound by it. Otherwise every time there is a change of contract that doesn't have to be notified to consumers the consumers would have to present the firm with a list of all of its previous undertakings and ask which, if any, of them it still intended to keep to for new agreements. You'll probably have noticed that changes are normally pointed out when banks update their agreements.

Complaint path for this would be ideally first to the firm, then the FOS in a specific situation or alternatively to the FCA's unfair contract terms team, whether there is or isn't a current dispute. The most relevant thing for the FCA team at the moment would be Lendy modifying its own obligation to pay interest each month on a loan it took out itself. No problem for future contracts, just past ones.