Healthiest / Best cooking oil

Hi,

I have light virgin oil and walnut oil in the house . i use a tsp of oilve oil when cooking & a 1 tsp of walnut oil over salads....

What your favourite / healthy oil to use?

Ive read coconut oil is good but Its £7 in my local sainsburys for 250ml! (Im from UK)

Ive been drinking a glass of coconut water every day as its really good for hydrating your body & its only 50 cal for 250ml (the one I drink is anyway).