Just be careful who you use, just because a car seems to drive well etc doesn't mean the map is good!
When I bought my MK1 daily earlier in the year it came with a "custom" remap done, the previous owner had a local company do it. One of these "specialists" who is mobile.
Decided recently to take the map off the car and have a look at it in WinOLS, stock turbo only capable of flowing 1.7bar max, map requesting 1.9-2.0 bar, SOI stupidly high amongst other things.
Companies like REVO,APR do hours of data logging on dyno's. They arent just looking at max power, torque, they are logging temps etc. I've been guilty in the past of talking bad of Darkside but the truth is they do remap very well and have a professional set up these days.
I've said it many times, an off the shelf remap from REVO/APR etc IMHO will always be better than 99% of "custom" tuners out there. You do get your exceptions like Darkside for Diesel, MRC for Petrol, R-Tech for Petrol etc.