Why has breast cancer in the UK increased by 30% in the last 10 years?

Could it be because less women are breast feeding, higher stress levels, more women smoking/drinking, more additives in food? I have no idea

Two reasons.

The first is that with routine screening and improved detection methods more cases are being diagnosed which may have gone undetected before.

The second is that because of improved health care in other areas, people are living longer; breast cancer is a disease largely associated with ageing, and 80% of breast cancer cases are women over 50.
There is no evidence that stress causes cancer or affects its progress in any way; the same is true of diet.

Edit** I have to respond to what another answerer says about dairy and Jane Plant.

Jane Plant is a professor of geology, not of medicine, so while she is a scientist she has no specialist medical knowledge.

At the time JP had her eureka moment, gave up dairy and saw her tumour shrink and disappear, she was undergoing a course of chemotherapy - common sense will tell you that the chemo had something to do with it!

At the time I was diagnosed with grade 3 stage 3 breast cancer I had been vegan for over 8 years - no dairy at all. Didn't prevent my breast cancer and sure as hell didn't cure it

It may not be that the incidence of breast cancer has increased...it may be that the technology and education have become more successful in IDENTIFYING breast cancer over the past 10 years. One has to be very careful of jumping to conclusions. You'd have to study the date to see what factors are at work.

I'm not saying the factors you site aren't at play, I'm saying they may or may not play a role and only more study would determine if and to what extent that's true.

Probably cos the hospital waiting lists are getting longer.I've heard of people waiting for months with cancer who if they could've been seen earlier would have had a better chance of surviving.

Maybe because detection rates have improved

recent studies suggest that because the life styles of women have changed i.e more smoke and binge dring also a bad diet that the cells in the body are getting mutated hence the cancer growth in women

It is because the detection rates are higher due to regular screening, and self examination.
There is probably no actual increase, just an increase in reported cases.

It hasn't. The rate of detection has vastly improved.

I don't think we are giving this dreadful decease to ourselves regardless what the medical profession tell us. I have a feeling this is due to Chemical emissions and the environment. Someone Somewhere know's something

The increase in breast cancer (I believe) is the result of the food chain! Interestingly enough in China and Japan the rate of breast cancer in women is minimal (neither have dairy products in their diets) but should they move to the west and live as western women (ie their diet) they have the same rate of breast cancer! As an ex BC sufferer, I have studied this in great detail. When you are told point blank that you have something life threatening believe me you find out every detail available. A book worth reading is 'Your life in your hands' by Professor Jane Plant an environmentalist who has survived BC 5 times....4 using orthodox treatments and finally deciding to fight it by diet and exercise. Another book also worth reading is 'Milk, the deadly poison'
*Just to say MCG...Jane Plant was not undergoing chemo the last time she had cancer and perhaps being a vegan was not such a good idea when so many nutrients can be had from oily fish.