You can normally get Spacer Units from the Dealer (and others) if the radio isn't a normal Euro DIN size.

I'm sure that CambsCar has some for sale.

Paul Haigh, 6GB, Blue
Reg: 4120 - Serial 00254
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Paul Haigh, Reg. 4120 (mk1) 6GB, Blue, 00254 (mk2) 12GB, Red, 00357