In reply to Sam Mayfield:
> The tv is only 2 years old date on the back.
Okay, so it's almost certainly using a switching supply.
> Tried to run straight from battery and same noise.
Okay, so it's the inverter, not the solar controller.
> The cable is fixed and straight into the back with a little cover with a scary sign on it.
Right: direct wired, no connector.
> Surge socket didn't work from the Invertor as the little lights didn't come on! Power went through but no protection.
Surge protection isn't a filter; it's to protect against large over-voltages. So it's unlikely to give you any improvement in the shape of the inverter output.
> So what's the cost for something like that?
A filter? Depends... haven't bought any for a while, so, off the top of my head, I'd suggest £10-20. My google-fu is very weak at the moment.
This looks like a reasonable website for explanations if you couldn't follow mine:
http://www.riello-ups.co.uk/ups-technical-support/line-interactive/
Think of your solar cells, battery and inverter as an uninterruptible power supply.
Wiki has a pretty decent explanation of the output waverforms you might expect to see.
http://en.wikipedia.org/wiki/Power_inverter
BTW, I'm not an expert in solar, battery or inverter systems, just answering with background knowledge as a electronic design engineer. So I'm only really speculating on what the problem might be, and what the solution might be.
If you have a genuinely 'pure sine' inverter (i.e. with a near-as-dammit clean sinewave o/p), and you're still getting a noise from the back of the TV, then something else is wrong.
What it the o/p voltage of the inverter, and what voltage is the TV designed to work with?
The other thing that bothers me is that an inverter sticking out very square edges will radiate all over the radio spectrum (generally considered Very Bad Form, and, in fact, breaking all sorts of RF emissions regulations), and it really ought to have an output filter on the thing anyway (internal to the inverter).