oxford, tec arc or portamig is there any particular model that is better or pretty much all the same?
Here is an example of a machine from TecArc that you probably don't want:
https://www.ebay.co.uk/itm/Oxford-2...elder-excellent-condition-No-Vat/264739434758
It is an Oxford "Migmaker". It does have a capacitor bank, the wirefeed has geared 2 roll drive ( but not 4 ). The output power ranges from 280 Amps down to 40 Amps, which is too high for you. The Seller reckons you can bring the 40 Amp low end down by using 0.6mm wire.
This model was apparently built by TecArc for Spaldings, an agricultural supply company in Lincolnshire.
From the auction listing, you can see how these machines hold their price.