Can anyone tell me roughly how much it costs to concrete a garden area in the uk?

We would like to concrete or pave (whichever is cheapest) a small insignficant area of garden measuring about 30 foot by 15 foot. It is currenly predominantly lawn with small paved path and is level ground. We dont want anything fancy at all just a straightforward hard area to use for use for random stuff like sand pit, paddling pool etc. but have absolutely no idea how much this might cost and would really like a really rough idea of likely maximum cost before we even begin to consider it. Whenever I ring local builders they wont even comment on a price but want to come round and measure up etc. first. I dont want to waste their or my time if the whole thing is way off our budget so please can anyone in England give me an idea of roughly what costs might be involved, I live in South East. Thanks.