Had my 184 FR ST (DSG) remapped a year ago. I had the REVO stage one map installed by an official REVO franchise:
https://www.onlyrevo.com/product-details/software/seat/leon-mk3-2012-/200/stage-1
Their figures suggest the remap makes around 214-233bhp, though I've not had the car dyno'd.
There is little difference in low down acceleration / off-the-line speed, but there is significantly more power / kick in 2nd and 3rd gears. It also pulls for longer (higher in the rev range), so the surge continues for another 1000rpm over stock. Nice thing about it it that it doesn't affect driveability, and still feels 'standard', though with more punch. No affect on the driving modes.
I've not noticed any change in MPG. It was never great (for a diesel), and I usually get 40-45mpg, sometimes just over 50mpg on a long run. I don't drive it that hard. I honestly don't know how some people on here consistently get 50+mpg with this engine.
REVO are quite expensive compared to other options I've heard about, but in my opinion when modifying the engine I didn't want the take the chance with anyone less reputable. No issues in the last 12 months.
I should add that this is declared to the insurer (REIS), no point chancing it should the worst happen.