Secondary Market Now Available

I have been drip feeding. This is not a test of the depth of the SM. I genuinely need the money and need to liquidate for other reasons. I'll be interested to see if my 1% discount generates any increased demand.

I assumed you hadn't drip-fed after seeing > £20k on offer at one stage, deep pockets of which I am envious!  The SM has been a moody beast these past few months with the massive cash injections from previous years ISAs, although discounts appear to be increasing of late indicating a slow-down.  Have you approached FS regarding increasing the allowable discount, they may be agreeable given your status as a HNW investor.

Don't worry, there are those 7 loans due to repay by the end of tomorrow, that'll sort out the glut.

Loans on FS pay interest at the end of the term only.

If the seller bought on the primary market they can sell without incurring any income tax liability so it may make sense to discount.

The buyer pays them the equivalent of the interest earned so far, the seller isn't liable for income tax.

However, the buyer is liable for income tax on the interest inherited from the buyer plus any interest they then earn.

Not sure how non-UK residents are taxed.

Two things:
1) tax, as already mentioned; selling before term accrues a capital gain and avoids tax on the interest.
2) risk: selling early avoids the higher risk of default the closer a loan gets to term.

If you need (or even if you don't credit cards give transfer to bank at 1.9% flat for 10 months at 1% payback per month.) If you need £1000 for 6mth it would cost £19.00 fee if your investment was at 15% (not too difficult) if you took off at the start the 5.5 month payment sell at -1% to insure no tax and money available to pay card back) you have to make at 1% a month you can guarantee payment to card.
works like this 
month 1 borrow £1000 (withdraw £1000 from FS you require)
fee £19 , total owing £1019
Total due in payment to credit card for 6 month is £10.19 x 6 =£60.94
Sum left to invest £939.06 (£925 if no interest bought so will work with this figure)
invest at 13% for 164 days = £54
sell at -1% = £9.25 (to be sure of sale and no tax)
interest left =£44.75
so total in FS to withdraw =£939.06 +44.75=£983.81
Amount left to pay credit card is the  original amount you had to invest i.e. £939.06
So you would be £44.75 per £1000 borrowed better off

you can repeat this for as long as you can and still have taken out what you needed. 
My mortgage currently £100000 costs me £960 interest only a year. I have money to pay this off but why
it makes me £12000 a year in interest £11040 after paying mortgage 
Make your money  work for you 😉