When the EPG downloads stopped, I replaced our DHD4000 with a Topfield, and decided to retire the Thomson to a flat we own in Bath, where DSO occurred earlier this year. A £20 STB had been functioning fine there ever since.
After setting up, a retune found NO channels, but I didn't give up, having read here that it might be necessary to try again. Well, after at least TWELVE goes, it found one MUX, with a handful of channels, so I persevered, and eventually it found two MUXes, with as many Freeview channels as we get in Bath (amazingly, for a major city and tourist destination, much of it is served by a repeater transmitter that used to carry only 4 analogue channels and no digital, and still gets only about half the Freeview roster, but that's another story!)
So the moral is: if you want to use your Thomson after DSO, and it doesn't seem to work, keep trying!