Can someone recommend one? Car is a Mk2 Octavia vRS 2.0T. Seen a link for one for a TDI but not sure if it would be right. It's capacity is higher than the standard one

http://www.ebay.co.uk/itm/Varta-E44-High-Power-Silver-Dynamic-096-Car-Battery-12V-77Ah-577-400-078-/271743143543?hash=item3f45274e77&clk_rvr_id=922214604700&afsrc=1&rmvSB=true

Don't worry about the capacity too much, particularly if it's over spec.  Main things to check are "will it fit my battery tray?"  and "has it got the right size & shape connection posts?".

I'm fairly sure the battery box in the engine bay is the same for petrol and diesel? If so you need size 096.

 

The Varta E44 gets rave reviews, it is a Bosch S5 with Varta branding. Great value for around £67 delivered.

 

http://www.ebay.co.uk/itm/Type-096-Varta-Silver-E44-Heavy-Duty-Car-Battery-77AH-SIZE-096-mercedes-/291213369073?hash=item43cdab5ef1:g:hOEAAOSwPe1T22Ui

 

77Ah and 780 CCA (Cold Cranking Amps).

Ta - ours gave up this morning in the cold so I bunged on my spare that I keep charged in the garage but will be off to buy a new one tomorrow - good to know the spec and dimensions