Guy has said on more than one occasion that Mark doesn't use a compressor in his signal chain (nowadays) but at the volumes he plays/records at, the natural compression of the amps will affect the sound. At "bedroom volumes" any reasonable compressor, delay and reverb pedal will get you in the ballpark for a clean sound. (or if you have a modelling amp, just play around with the effects). When it comes to a distorted sound, you would be better off with an Overdrive pedal than a distortion pedal for most of Mark's "distorted" songs. (and a Les Paul of course).