I have always been super active. Until recently I was living in Hawaii, working on my feet all day, jogging or biking to work, the beach, other towns.. Swimming and running rocks to shore daily. It doesn't matter what I eat. When I was eating super healthy my cholesterol was over 500 (13 For you in UK). After moving and getting a desk job, not able to be as active but still renovating a home and exercising daily, slipping on my diet for a while, still 500 (13). I didn't even know about it until shortly before I had a heart attack at 26. Statins help very minimally because they assist the receptors that (eli5 version) recycle your cholesterol from the blood.

Imagine you have a restaurant, say a buffet, and you have 150 seats that always need to have a plate. Each plate is cholesterol. To make sure all guests have a plate you own 150 plates total. When plates come up to the window (receptor in liver) to be washed you take the plates back and recycle them into use.

Now sometimes plates fall and break, or get stolen (cholesterol leaving the body via urine or whatever) but you MUST maintain the level of production, so when 30 plates break, you make 30 more to supplement. If people bring outside plates in (eating a very fatty meal) you realize and take them out so you have the correct number again. That's basically your body peeing out or using up cholesterol, and regulating your levels by producing more when needed.

But what happens if your window is closed(receptors don't function)? Well then the kitchen doesn't know how many plates are needed. It just knows that people still need an expected amount of food. So instead of letting the guests starve, the kitchen keeps ordering more and more plates, sending them out. But no plates are coming in due to the closed window, so hundreds of extra plates get made. Some will get broken or stolen as before, but not enough to even out to 150!

So statins basically help (very eli5) by adding a worker at the receptors who can grab some dishes and shove them through small spaces in the window.

If you have familial hypercholesterolemia, the window doesn't have as many small openings. So those statin employees can't help very much. You need a different drug that just tells the kitchen "hey... We are always overstocked by about 400 plates. So let's just send out 20 plates at a time. We will lose business, but the extra plates won't fill up the dining area and the restaurant will live longer.

There are multiple types of familial, and at your level it could be hefh, where one receptor gene is faulty but the other gene is fine. In that case it's like you have two windows, and one works. So an employee (statin) might be able to mitigate the damage. Hofh means both are broken, so the statins won't do much still.

Anyways if you don't have a med for it you should check into it. I had a major heart attack at 26 and my 3 year old son has 300 (8) as well. I am on a very very expensive and rare drug and have done more than my share of homework on it. Just remember you might not always be able to be as active as you are now, life is full of surprises... So get that level down under control before that happens so you don't end up with an uphill battle to stay alive. Because it really sucks!