I've used my diesel on track days, albeit my previous one.
Get track day insurance. It's invaluable! A good friend of mine stacked his diesel on track and it was game over as he had no insurance and no daily car!
Diesels are great on track, especially if you do have a fast one, a puff of smoke as you overtake someone is great for upsetting people
Don't worry about it being a 1.4, just go out, have fun, be safe! Once u know you enjoy it then u can look at a purpose built car or performance mods to yours.
Factor in fuel and new tyres to the cost of the track day and insurance. Also any helmet hires etc...
ok, the tyres is something i am unsure of. how are the tyres affected? how many miles roughly would they last driving on a track?