I think its more a case of the way the market is at the moment gav - with only Boyles and a
Betfair market its all very weak, and I doubt Boyles have lengthened any of the runners regardless of the songs released...they really just need any old price up(provided its not too big) to sweep up a few patriotic bets here and there.
So from their point of view they aren't 'making a market' as such, just taking advantage of being the only bookie with prices up.
Betfair market moves are happening in slow motion given how thin it is but i'd give it a week or so to creep slowly but surely up.