Extending aerial from cable tv downstairs to new freeview tv in bedroom can it be done?

Yes it can but with a few conditions:

If two televisions need to run on the same antenna feed, then a splitter will be needed. These are either passive or active. If you have a clean and string signal, a passive splitter will be fine. You can normally find out the signal strength by looking at the set up or diagnostics menu on a television. Most have an indication of the signal strength and quality for each channel. If they all show a very good signal, passive splitters should work fine. If the signal is moderate or poor, then an active splitter will be needed. The splitter will need a mains power supply and will amplify the signal. Normally they will have two, three or four outputs.

If the aerial feed simply has to be moved, then the cable can be extended using suitable RF connectors. Note that the cables cannot be twisted together or joined using a terminal block.

If parts are needed, try to buy them from a local aerial specialist. They have the experience to tell you what you will need for your area.