Cheers guys!
As I've had a couple of responses asking where I got the supplies...
The magnets were from eBay shop
NeoMagnetMan. They are the neodymium N42 20mm x 5mm discs which are £7.29 delivered. Looking at the specs I assume they are the same ones as sold on e-magnetsuk.com (item 336).
I used Araldite epoxy resin to stick them to the plates and to the rear of the grill. Again, I picked up some from eBay for £4.49 delivered but I would've thought you can find it in most DIY stores.
The new front plate was from eBay seller djhplates and was just under £6 delivered.
Hope this helps!