Liquidity

Zopa has good liquidity because the loans go on the main market but you pay a percentage fee and also you take a capital loss to get the buyer to the current market rate. If there is a capital gain, Zopa keeps it or uses the higher interest rate to let them discount other loans that the buyer is making, to hit their target lending rate, which in turn allows Zopa to charge a higher lender fee.

RateSetter is similar to Zopa in the main market aspect but worse because you not only get the interest rate matching cost but also they change the market involved, so your capital loss is likely to be larger. If there is a capital gain the money goes to the protection fund rather than directly to RateSetter. Indirectly it allows RateSetter to have lower charges for the borrowers so you're probably subsidising both RateSetter profits and other lenders indirectly.

Ablrate has decent liquidity provided there is not a relatively big seller in front of you, up to a few thousand or tens of thousands per week depending on loan size and the price you're willing to sell at. If you push the price to the limit it can take a while to sell. Not same week liquidity in the millions or hundreds of thousands range but for tens of thousands well diversified it's pretty liquid. More long term dependable liquidity than the par-only sites because you can price to deal with interest rate changes or demand.

Bondora has a generally excellent secondary market but there are too many reasons to avoid Bondora for me to suggest using it, particularly given that I'm choosing to disinvest for those reasons. You can set discounts or premiums and that can help loans to move if it's not fast enough for your taste.
You can't trust Bondora's projected returns and account values because they are distorted badly by the default and other impaired loan reporting, which combine to keep showing people good results on their investments for several years after things have gone bad.

Since Zopa and RateSetter are offering substantially lower interest rates Ablrate is probably one of the preferred options to use in your case.