Do I need a dealer battery for this or are they available in likes of supermarkets etc?

Car complaining that I should replace battery as low.

As long as changed quickly I take it they don't need reprogramming.

Get a decent brand as cheaper brands don't tend to last too long. I've just ordered Duracell batteries for mine.

I think they are something simple like a CR2032. Easy to change, should say in the manual.

Panasonic are also a good make of button batteries.

Cheers will have a look for duracell or the likes later and check manual (at work just now)

CR2032, any brand will do and they’re about 50p. 
I get mine on Amazon

Any brand will do but some last longer than others. The poundshop ones are rubbish, JCB are also cr4p. I always go for Panasonic myself.

I buy in bulk as the 2032 batteries are fairly common in many electronics devices (especially for video/camera gear). They last a long time n storage so always worth keeping a few around. 

Thanks bought Energiser ultimate in Asda was £6 for 2. Changed it and works OK. Decided I'll use the spare fob now which feels great as brand new still. I'd guess that battery might not be too far behind due to its constant emitting signal for keyless entry. Hopefully go a little longer since buttons havent been getting pressed.

Wow you got it sorted but that’s crazy the prize. On amazon you can get 10 for £6

Suppose it is quite dear in comparison but original battery has lasted 3 years, so might not even replace them again while I have it.

True. For my £6 I have 9 spares that I will struggle to use...false economy of some kind. 

12 minutes ago, The Finance Guy said:

True. For my £6 I have 9 spares that I will struggle to use...false economy of some kind. 

Split the cost with a friend, or start a business selling them. Capitalism at it's finest. 😁