If you just want codes any cheap code reader will work, but its just generic OBD codes. I have a £20/£30 quid ebay one, it can do basic monitoring as well, eg TPS, MAF etc, handy for pulling a code without getting out the lap top.
If you want to change coding on a T5 I would use VAG COM VCDS, genuine from ross tech, or an illegal ebay clone for about £50, just dont update it.
VCDS is also much better for diagnostics, logging, output tests etc. Loads of support and info online as well as on Ross Tech.
OBDeleven is meant to be a VCDS equivalent, but I have no hands on experience of it. They do sell coding apps if you dont want to manually change coding.
Garage is more likeley to use Snap On Solus, Modus, Autel Pro range etc, but they are £££.