Where did you buy your TV from, if not direct from Sony you should contact whoever sold you the TV directly.
A few high street or on line retailers offer multi-year warranties and you may have bought your TV from one of those, John Lewis or Richer Sounds for example.
If you did by direct from Sony you will normally only get a one year warranty but it may be that at the time of purchase your model of TV was eligible for Sonys extended 5 year guarantee, can you remember if you checked and applied for this within 30 days of purchase.
It is possible you are covered under the Consumer Rights Act, so try contacting Citizens Advice.
Three red blinking lights could mean there is something wrong with the supply of power to the TV.
The TV may have gone into over protection mode.
When trying a reset have you disconnected any devices connected via HDMI or USB as these could be causing
the issue.
Have you tried a forced factory reset, instructions here,
https://www.sony.co.uk/electronics/support/articles/00274122
Follow the instructions for one button TVs.
If the resets don't work then there is a malfunction on one of the PC boards within the TV.
A repair person would need to be called out to diagnose the problem but please do not do this
as this would negate any warranty (if there is any you have on the TV) and would disrupt any case
you would have with Sony if you decide to involve Citizens Advice.
More than likely you will have lost the use of the TV over Christmas, do you have another TV you can use.
