Hay fever can be inherited together with other allergic conditions such as eczema and asthma but food sensitivites, such as wheat and diary, can cause problems as well. It may be worth consulting a good nutritionist.
Pollens are produced in the United Kingdom from February to September. The concentration in the atmosphere increases as the weather warms up, peaking in July. It's often in the morning we feel it, when the pollen is carried into the atmosphere by the sun warming the air, and in the evening when the pollen laden warm air descends.
The good news is that once you find a remedy which works for you, generally you're ok with that one for quite a while, season after season.