There are no emissions-legal manifolds that deviate from the stock design. I don't know if they do testing or anything there in UK for that, but in any case there are no high-flow aftermarket cats or test pipes made specifically for the d16y7.
There are plenty of headers made that will fit, but they are made for the VTEC model and will relocate the converter down under the car so you would have to get the converter made for the sohc VTEC (in the US it is d16y8).

Also I'm confused, you said you have a "coupe 3dr". 3dr here is the hatchback model and coupe is the 2dr with trunklid...I mean a "boot"!!! This determines what "catback" exhausts are available for your car.