i stay in India, so well don't really have ideas of England.
Here's my two cent on it though:
You talk to them , they think from the word 'go' , you're trying to pick them up. They look for clues(thats my opinion) in your convo to the effect.. They shoot you down with the mentality , that how dare he pick me up? Does he think he can pick me up ( read :is she easy ; ASD)
If you wanna , well , be real indirect about it . Very few girls are open . Most will act all fun and flirty, but rememmber , they'll usually hesitate in moving things forward.