PCA does all this in his own time - he sources all the parts, and designed a new tuner just for us. He's not exactly making a lot - if any- money from this

Well, he's:

- not making any money at all, and has to invest masses of his own, unsecured money (GBP 4,000+) to buy bulk batches of tuner modules, leaving himself way out on a limb

- ordering, sorting, and bagging the whole thing up himself (many hours work for even small batches - think of the number of components)

So I reckon the relatively modest price he's charging (GBP 110? Not sure now) for the unbuilt kit is actually ridiculously underpriced for what you're getting.