It's impossible to answer your question without knowing a 'starting point' for your rent.
If, for example, you're living in a tiny bedsit and your rent has gone up from �200 to �280, that's a 40% increase and obviously well above inflation.
If, however, you're living in a house where your rent has gone up from �1000 to �1080 per month, then thats only an 8% rise over 3.5 years and probably below average rises.
Another thing you could do is to have a look in your local paper. You should be able to see the kind of rents other landlords are asking for similar properties as yours. This should give you an idea of if you are paying the market rate.
Cheers
As others have said depends on the size of the original rent. I rent somewhere for �1060 a month the original rent was �1000 and we have had two rises for �30 each year.