Thanks Alan,
OK, I thought it may be wise to change the brake fluid, but didn't know if I was doing an over kill.
I think I have found the date code and it is VDB3705. I am not sure if that is the code or not, but I am sure they are the original Bridgestone tyres when the bike was originally purchased in 2005.
There is plenty of tread. Why would you think there could be an issue with these tyres?
John