http://esupport.sony.com/CA/p/select...pl?PRODTYPE=74
Firmware is included in Drivers & Software. (see right side to choose your model, etc)
Note: this is the Sony Canada site, I don't know if the updates would be any different for you in the UK (I assume the US and CAN are the same, but don't know if Europe has variations).
But, as others have said, if they are working and there isn't a new function added that you want/need, why bother updating?