Bailey performance has got a very good Rep if your just looking to get it done.

http://baileyperformance.co.uk

Making up a loom is easy. Just take your time and do one circuit at a time. Mapping it is another story.

Oem is much cheaper but more time intensive. No mapping needed. Just turn the ignition and go. But not very flexible.

I wouldn't bother with pre pats. Pats is easy to use and gives obd2 functions for fault finding.