Just found the info below on a website - it appears that its just around the 10th anniversary of the UK photocard introduction so a lot of them are starting to expire.
Appears that a UK licence is valid up to 70yrs old regardless of the photocard but you can be fined up to €1000 for driving in the UK with a photocard with an expired photo!
Photocard Driving Licence 10 Year Update
When does yours run out?
All UK photocard driving licences need to be updated every 10 years.
The photo on the licence is only valid for 10 years, therefore the driving licence and photo needs to be updated accordingly. Drivers will not need to retake a driving test but will of course need to submit a new photo of how they currently look.
This will start to happen from July 2008 onwards, the DVLA will start to issue reminders from May 2008 onwards. The holder must renew their licence before their current photo expires. Renewal is necessary to avoid a £1000 fine. The licence expiry date can be found in the section marked 4b on the front of the photocard.
The paper part of the licence however does not contain an expiry until the holders 70th Birthday.