Any question answered...

I'm not sure you have any legal rights once the provisions of DSRs are out ie after 7 days, if the goods are fit for purpose.
The situation will be governed by the contract you made w the seller which will essentially equate to the t&cs of their website at the time, assuming they had one of the tick boxes where you agree you've read them.

if <7d return postage is the sellers responsibility regardless of the reason for return but this is often flouted

TL;DR:

Restock fee not allowed
Period for cancelling the contract is 7 working days from delivery, not including weekends or bank holidays.
Notice by email allowed.
Seller is responsible for organisation and cost of retrieval. Cannot insist on undamaged original packaging.
Refund should total 100% of sale price and delivery/packaging fees except giftwrapping, express delivery

From the website: http://dshub.tradingstandards.gov.uk/explained

Refunding the costs of return depend on what a customer has been told and agreed to at the time of sale. The customer can be made to bear these costs if this is included in your contract terms and forms part of the information required to be given to customers

I'm intrigued as to what you're both saying. The bold bits in your posts don't match my interpretation of the text I've included above.