Any good tuners near Derby
I know of one, but it may be against forum politics to say it out loud on here.
Which is the best remap for performance and can it be reset back to original
I'm sure any of the tuners could advise you about that one.
Do you really get better MPG than the standard map done by VW engineers
Yes, when driven normally, but when you use the performance, you will obviously use more fuel.
Does adding 25 bhp make that much difference on a car weighing 1400kg
It's all about the torque.
Do you need to change the air filter as well
No. The standard paper filter is more than up to the job.