Lens and converter for sale

Hello folks, I've decided to get rid of my camera lens.  Since the demise of the camera body I haven't missed using it and have realised how much it was taking over my birding.

So if you or anyone you know is in the market for a new lens let me know.  It's a Canon 300 f4.0 L IS USM and has a 1.4x extender with it.  It still retains autofocus when using the extender.  They are both boxed and have cases.  They are both approx 29 months old and in very good condition.  I'm looking for around £850 for them.