Ugh! Decking/patios everywhere! How much to get rid please?

Depends on how much free labour you have available to you. If you have a moderately muscular bloke with a sledge hammer (40 for the hammer ) then you could fill a skip (150 for the skip) with a large amount of concrete/paving in a day. Paying somebody to remove it for you will cost per day's labour (60 quid or so per man).

Lawns can be pricey (several hundred, at least) - particularly if they need to do a lot of soil preparation. If you've broken up paving and/or concrete then there's probably a layer of hardcore beneath it that needs removing and then replacing with topsoil before you'll get a decent quality lawn going.

You can buy the soil and sod yourself and then lay it, but that is backbreaking work - those rolls of sod are astonishingly heavy, and they all need carting out and laying and treading in. Check here for prices.

A lower labour but longer lead-time method is to buy a mixture of topsoil, compost and grass seed like this - then you just spread it, water it and wait. It takes a couple of summers (drought free) for your lawn to thicken up properly.

Or you could buy artificial plastic grass. But then you'd go to hell. The hell for those with no taste.

Many London gardens don't get enough sun for a decent lawn, and are also on very heavy clay. Beware or you could end up with a muddy pit for a garden.

Sometimes there's a good reason why it was paved over in the first place.

Agree with ib. We partially decked our London garden because the lack of sun / clay-heavy soil mean a lawn would be very hard to maintain. Double check before you make a decision.