I too have observed FGW▸ policy re advance fares.
For the last 6 years I have each month travelled from Bodmin to Bearsted and returned twice a month. I travelled out on the 0806 from Bodmin and usually come back on the 1406 from Paddington. There was a sudden price hike just prior to the Olympics that has been sustained and indeed got worse. I usually was able to get tickets for ^17.00 one way making a total cost per month of ^68.00. Now on any train on the Thursdays I travel the cheapest advance ticket is ^53.50 making a total cost to travel to work per month of ^214! This cost is actually only 50p cheaper than an Open off peak return.
I've just checked at random - Wednesday 20th March, and there's a 17.50 ticket available on the 19:01 train, getting to Bearstead at 06:39 on Thursday morning. There's also a 29.50 fare on the 17:21 (00:15 into Bearstead), and 36.00 on the 23:06 sleeper getting in at 07:49. Plenty of tickets at 53.50. On my own "home journey" - London to Melksham, I am quoted 8.50 on the 23:30 train that day, which involves waiting on the platform at Swindon from 00:47 to 06:12, with other fares starting at 41.00.
As train travel gets ever more popular, and people get more used to looking around for better deals too, the best bargains will have become harder to find, even if they're sold in the same quantity they were sold in before.
I don't know of any source of information which tells us how the numbers of tickets in each bracket for sale (and actually sold) has changed, and I'm not actually sure what form the information would have to be presented in to convince us / me that it provided straightforward information ... can anyone help with this? Perhaps one of our members who works for FGW could follow up with some figures?