Mirrors with radius 450mm (under the old directive) have to be replaced with glasses with radius >300mm (under the new directive).
In most cases it will be sufficient to replace the glass unit only, there may be cases where it is necessary to replace the complete mirror.
Directive 71/127 EEC (old directive)
For mirrors which only comply with the old directive a large area remains invisible on the passengers side.
Directive 2003/97 (new directive)
The field of vision for the new directive not only improves the vision on the passengers side, but also on the drivers side, through the wide angle mirror.
If you need anymore information please feel free to PM me, I have a contact who may be able to help you further.
We've just had ours done on our Y reg lorry. We already had the wide angle and kerb mirrors fitted so asked our mechanic to check that they were legal when it went in for servicing last month. He replaced both the wide angle and Kerb mirror. It was less than £100 for both mirrors so not too expensive and they gave us a certificate which we will have to produce when it is tested. As to why they replaced them, the mechanic gave us an explenation at the time but i can't quite remember now, i think it was something to do with the Convexity??!! of the mirror and i have a feeling the wide angle one is heated too?! I'm hopeless when it comes to lorrys, if you send it in to any commercial mechanics im sure they will be able to tell you!!
A mirror that is attached above your passenger window looking downwards, with 300m curvature
Your normal mirror
And a wide angle mirror that goes either above or below your normal mirror on the passenger side
You may also need to buy a new mirror arm as I couldn't fit the wide angle mirror and the normal mirror on my old arm at the same time.
How old is your lorry if it was first registered after 2000 you need the above, if it was registered after 26th jan 2007 you also need a mirror on the front of the windscreen