Pricing old figures

Morning (well here in the UK anyway)

I'm wanting to sell off my old GW figures. They are all from the Epic
range of
about 4-5 years ago.
They are all painted and based. The infantry stands are even flocked!
The paint job is of a wargaming standard, more so in a lot of cases.

Now my trouble is I have no idea of their current worth.
How do you go about giving this sort of thing a price.

Being GW they cost me an arm and a leg originaly.
I mean £3.99 for a super heavy tank! and now they are
painted does that add or subtract from a possible cost?

Any advice on this would be great

cheers
 
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Jeremey Claridge