Considering they want £300 per person for return flights London to Murcia, in August, I would hope that they will have the seats on sale at some point.
From around mid July I was looking at various airlines for October half term flights & they were all so expensive that we almost decided not to go. Then about 4 weeks later I checked Ryanair again & the outbound flight was only 79p & the return one was £49.99. This resulted in a total fare of £100.75 each, when at the beginning of my search they were almost £200 each.
A couple of years ago, we booked about 6 months in advance to go to Dublin at Easter & we got 1p flights - there doesn't seem to be any set pattern with Ryanair.
It is a bit of a gamble when to book but it does pay to keep checking.
Noreen