Its a race track, people go to race.
As on the road, sadly you cant legislate for morons who might get carried away.
I think you are mistaken Ian Mc, you are not allowed to RACE on a track day. You are only allowed to overtake on the straights,and only on a predesignated side. It is upto you to drive at whatever speed you are comfortable with. Obviously if you drive at 40mph and don't move out of the way for faster cars then you will wind up other drivers and also be black-flagged by the track-day organisers and told off or excluded. Obviously i'm talking hyperthetically,as some people are going to flout the rules,but I have done 1 track-day and never felt intimidated or scared by other peoples driving or attitude. I would advise you to pop along to the venue you are looking at attending next time the have a track-day organised and see how things work. Talk to some of the drivers and officials if they aren't too busy,and you should get a warm welcome and some good words of advise.
I would still advocate getting a car to do track days in,but maybe have a bash in your normal car for a start and see if you get hooked.
As for saying "do they break easily",then you are stressing everything on the car way more than is possible on public roads. Brakes are the main cause of issues from what I have seen by popping along to my local track. They can be cooked in 3 to 4 laps of hard driving. I cant be driving mine anything like hard enough as mine never got anything like hot,but they are the bigger AP brakes. To try and do anything like reasonable lap times you will also be pushing the engine into the red-line,and your fuel consumption will be scarily bad. I wasn't really pushing hard on my 1 day,but had to fill up again at lunch break! ( And that was only after 4 or 5 15 minute runs.!)
Where are you looking at attending? I would go to somewhere with plenty of run off. I go to Blyton Park,as its only 5 miles from me,but also because there is only 1 chicane with any Armco barriers close by. All the rest of the track has lots of run off to allow for mistakes. My goal is to go to Cadwell Park. No run off and seriously tricky to learn. I would think Bedford autodrome is closest one to you. From what I have seen its an airfield circuit with lots of run off. Pop along on the 18th of Feb and have a look.
Hope this helps. Rob.