Yeah I've not heard overly brilliant things about scooby clinic either, API seem ok but they like to sell you stuff you likely don't need. Whereas Mark will ask what spec YOU want from the car and suggest the means to getting it. Eg I now need around £4k worth of additions to get from 315bhp upto 420ish.
One good point is that he's good at mapping vehicles, so you're not having to pay for someone to come in to do the work like API who don't have their own individual who can map an ecu which always costs a great deal more.
The other one to watch is the likes of fast !Removed!, whilst a couple of them are nice lads, they're not specialists or highly experienced. For example they set up the suspension on my WRX without using the camber adjustment on the top mounts which causes the wheel to catch. Almost highlighting the lack of experience and knowledge in how things should be set up.