You have not said which Thomson model you own. From the issue that you describe it may be the Thomson DTI6300.
The are two schools of thought:
(1) Replace some of the capacitors on the power board
E.g. http://forums.digitalspy.co.uk/showpost.php?p=40306912&postcount=13
For the parts see http://forums.digitalspy.co.uk/showpost.php?p=48394014&postcount=12
(2) Leave it a bit (sometimes 2 days later) and it may come to life.
E.g. http://forums.digitalspy.co.uk/showpost.php?p=32921764&postcount=13
E.g. http://forums.digitalspy.co.uk/showpost.php?p=48010955&postcount=10
E.g. http://forums.digitalspy.co.uk/showpost.php?p=50356576&postcount=10
Both methods have been reported sometimes to work. However, there are reports that having replaced the capacitors it appeared to work OK for a bit but it was all a coincidence and the fault was still there. And if you do nothing then it obviously could occur again.
While I have fixed other models of freeview recorders I would personally give this one up and replace it.
With the demise of TopUp TV you may well find a replacement 2nd hand Thomson available cheaply. Just take care that you are not being sold one with the same fault.
Wishing you the best of luck in your difficult choice.
Neil S
November 2013