BMW tyre pressure sensors

[Gixer968CS]

I have a 2013 BMW R1200 GS and it looks like the batteries have run down in my tyre pressure sensors. Cheap ones on ebay, but I'm not confident of fitting them myself (or able to remove tyres), or if they would be any good and getting my BMW dealer to do it is looking like £400+. Has anyone dealt with this issue and found a decent cheaper way of getting it sorted - for example is there an independent that'll do the job more cheaply (I live in Kent)?