The HEL shuffle fares are also available to MAN or JER as destinations for about £550 for 400 TP. For example between 22 and 24th March (the dates I've been using). You can also slide in OTP as the sandwiched destination for 480 TPs for about £680.

Obviously bear in mind the cost of two nights in HEL can be significant, but on the timings I was working to it's feasible to stay somewhere in the airport for 5 hours, shower in the lounge, and sleep on the way back.