I got so fed up at never being offered the rate online that I sent an email, basically accusing them of fraud. In a reply they said the best chance of getting the rate was to do a phone booking and they would advise what was available.
What I asked them was why they didn't have a matrix on line similar to that of Travelodge, with whom I have never had problems getting the cheap rates.
Hi, just got back from 5 night stay at Yeadon Premier Inn near Leeds at £29 a night and got one at Plymouth Premier Inn in May for 2 nights same price, so they can be found and in the places you want to go. I usually look at Premier Inn, Travel lodge and Inn Keeper's lodge and one of them has an offer on at the time and place I want.