Cat C damage may be light but unless you know what the damage was then you will struggle to decide if this may have left a lasting impression on the vehicle.
I've seen what the trade considers a "light frontal" and the suspension has been moved. Really, I'd not want to get into it with a car which has had that kind of movement. With the fact that cars are more and more designed to deform to protect the occupants you will find surprisingly light damage on a modern-ish car will lead to structural movement.
OK - you want to buy a car, you find out it is Cat C, you get the HPI report and you find out when it was done. As said above, a Cat C wreck on a nearly-new car and you should walk away IMO. The damage will have been extensive and unless there is an engineers report of extensive recipets to show this was correctly repaired you are just guessing and hoping.
It will always be worth less come resale as is shown in this thread, some people hold very firm opinions on register recorded cars. Someone good with maths will show you how it is often better value to buy something more expensive but which devalues less.
Your call.
I've owned damaged-repaired cars before and they are a mixed bag. Some good, some not so. Not just the risk of them falling apart in another accident, touch wood, never happened to me, but stuff like uneven tyre wear you can never get sorted out no matter how many times it gets tracking, allignment, etc. leaks, whistling noise at certain speeds, etc. just stuff like that.