Only just seen this thread.
I know that recent tax changes has led to various bookies looking at mergers, my (very layman) view is that if the market is squeezed for options resulting in less choice then it can only be a bad thing for punters.
There's no question that punters have had a great 2/3 years of offers for Cheltenham and a few other festivals as bookies fight for business, the problem is that high st bookies only want a specific type of business, machine punters and 50p yankee/union jack players.
I don't know the answers but the SP system is dying on its' arse as a result of the exchanges stealing 99.9% of the market for every race day bar a few select few, on course bookies are barely covering costs and are falling away day by day, SPs could easily be set by 2 bookies who haven't taken a bet all day, it's a mess.
Where it all ends up I have no idea....