If all you're towing is a little MX5 then you don't need a huge great 4x4 or pickup. Grab a Volvo 850/V70 for £notalot as it will do the job nicely. My 850 estate did admirably towing my old CRX on a BJT Clubman.
I agree completely. The last few years I've been towing a big BV105 box trailer around the country with an Octavia 1.8t 4x4. Fully loaded it was probably between 1.2 and 1.4tonnes (sometimes more) - and being over 7ft high it's a massive wind break behind the car. It did the job admirably. This year it'll be towing the racing car on a BJ minno max and I it will be even easier without so much wind resistance!
It doesn't seem worth buying a big 4x4 or pick up just to tow the race car on say 10 race weekends a year - as the rest of the time it's a big compromise.
If you get yourself a big estate with a decent engine it'll tow brilliantly, take all the spares and will be comfortable to drive the rest of the year.
It's nice having the 4x4 system on the octavia (mostly as it adds 100kg to the weight of the car) but it's by no means essential.
Do invest in a decent trailer however as that often makes a bigger difference than the tow vehicle. A good Brian James or Woodford should hold it's value well.