Welcome to the forum Luke.
Nice looking A500 that you've got your hands on.
TMC fitted to a Esseesse model can be fitted to a standard A500. There is an old version and a new version with the latter version have 2 connections as opposed to 3. One is easier to fit and remove which needs to be done before a visit to the dealership.
There is also a newer version where the 'mapping' can be done by remote with a 0-1-2 stage. This idea originated from the U.S. although it supposedly can't be done whilst the car is on the move but it's also pricey. It was designed to increase the outputs on the US model fitted with the garrett turbo with 160bhp standard to 200bhp.
It is hard to beat the £ per bhp improvement of a tuning box. It will give an additional 15 bhp increasing boost from 0.9 to 1.2 bar. Note the boost gauge will not read correctly since the mapping is tricked. The gauge fitted in the A500 is electronic but it can be changed to a mechanical one so that it gives an accurate readout.
Another option is to get a A500 ECU - get it wiped and put a new map onto it keeping the original intact. On the original esseesse kit it came with a esseesse ECU that replaced the existing one. This changed at a later stage with the A500 getting remapped at the Abarth garage. It caused one particular gargage in NI some difficulty on the 'upgrade'.
Some change to a BMC air filter which is along the same lines as a K&N cotton gauze filter which might add another 1-2 bhp.
From the figures that I have seen on the torque outputs - the TMC is slightly higher than the esseesse model but both exceed 230 Nm which is higher than the rated output for the C510 gearbox at 206Nm.
If you opt for the TMC you will have you use higher octane fuel which is still benefical on the standard model.