Try adding some chilli sauce. Mixed with the olive oil and fish it's amazing. After experimenting with quite a lot of chilli sauce with mackerel/oil over a period of years, I really recommend "Encona West Indian Hot Pepper Sauce".
If the 'sunflower oil' etc versions of the mackerel are available it also mixes extremely well with those and they can be cheaper than the olive oil tins.
Agree on all counts except the sunflower oil. In general, avoid seed/vegetable oils, especially if they are used in high-heat cooking as in this example.
Vegetable/seed oils are not whole foods or naturally stable. They are modern frankenfoods made from leftover agri-waste via industrial chemical processes. Under high heat these oils become highly oxidated and not the kind of stuff you want your body to deal with.
Comparison of the oxidative stability of soybean and sunflower oils enriched with herbal plant extracts (Kozowlski, Gruczyńska, Chem Zvesti. 2018; 72(10): 2607–2615.)
If the 'sunflower oil' etc versions of the mackerel are available it also mixes extremely well with those and they can be cheaper than the olive oil tins.