Daniel: I understood Philip to mean that the charge was £25 max for labour charge for the entire repair (irrespective of the length of time the repair takes). This is clearly an attempt to stand out against the competition as providing a cheaper service. Of course, parts are chargeable on top of this.

As Philip's job was reasonably lengthy (taking three hours) obviously this is a case where the £25 labour charge does not favour the repairer, who would be making an equivalent of £8.33 per hour. To make up for this he was overcharging for parts. In Philip's case he was overcharging by 5 times.

So, for example:
The repairer charged:
£25 for labour
£40 * 5 = £200 for parts (this being the parts value, multiplied by five)
-> Total = £225.

Comparing this to somebody who overcharges by three times (something Philip suggests he would find acceptable) and the equivalent labour rate for the same total price would be:
225 - (40 * 3) = £105. (Or £35 per hour, if you prefer).

In summary, the repairer was shifting the cost from the labour charge onto the part charge. This could be rather misleading as (a) his advertisement falsely suggests a cheap service and (b) the person seeking the services of the repairer can budget for labour charges (though possibly not the number of hours labour required) as they are known up front, but they are unlikely to be able to budget for part charges as (i) they may not know what parts are needed before the work commences and (ii) they most certainly will not be aware that the part charge is inflated by five.

Considering this, I think it was perfectly reasonable for Philip to find the (overall) charges unsatisfactory.

Philip: Please confirm I have understood your message correctly.