Hi,
you should contact the council about this. as they have the responsibilty for your street. You may even have to seek planning permission to remove ( pave over ? ) your front garden. This is because of recent concerns with flooding and lack of drainage as gardens soak up excess water and paved areas don't.
You must have an understanding council One of our relations had to pay the council �1000 to get their own workman to lower it. The get out for them was if someone tripped on you DIY job you could be sued.
you might not need plannig, but what about a vehicle access licence? Before you go digging up the highway you should consult the streetworks section and you will need to consult the statutory undertakers (elec, gas etc)
I can only second what kwicky has said, as our council told me we would need indemnity of several thousands of pounds in case any one injured thereselves on it and made a claim, needless to say, we let the council do it, but i guess i was fortunate because it didn't cost anything like the prices being quoted here, but then that was twenty five years ago, and the sue everybody fever hadn't started at that time