Licence Entitlement

My son took his CBT a few months prior to 17 on a 50cc and has his
provisional driving licence.

Good.

He has now reached 17 and has bought a 125cc Honda motorcycle. Do we
need to do anythin with his licence to update it - or is this already
valid as hje has now reached 17.

He's OK

The photocard licence does show a small motorcycle picture with the
valid from date stating his 17th birthday date and the ending stating
his 70th birthday ..

Exactly

Get him to do his test as soon as possible, the new test in October is much
harder and more expensive. There is also talk that the CBT could be a three
day course.

Thanks for any help

Don't think so. The licence will be a provisional for a 125cc bike so just
keep using L plates. Remember, the CBT pass only lasts 2 years so he'll
need to take the full test before his 19th birthday or he'll have to do the
CBT again.