Is it at all possible for the top soil to go over the other side of the garden? Top soil tends to come in 1 ton bags which would involve removing from the bag into a wheelbarrow, through your house into the garden. That is very tiring and will take a few days and tons of top soil. Most delivery trucks have winces that move the bags, so could potentially go over a wall directly into the back garden (if not surrounded by other gardens/cliffs etc).

How much top soil are you planning?

Kildermorie, I think Guy is saying its the turf that he'll be buying in, not topsoil, unless I've misunderstood the question.
Actually Guy, the optimum time for turf laying is October - provided we're not waterlogged or frozen, but if you're not going to be ready in time, then laying in March (again, with the caveats already mentioned) will be fine - but you will need to keep it well watered, so prepare for a hose and sprinkler to be easily accessible, particularly during April.
I'm not sure I'd bother to remove all the turf if the area concerned was going to be buried by 6 inches of more soil - I'd remove it if it was only an inch or so, but not deeper. Any turf you do remove should be stacked grass side down and left to compost slowly over a year or two, when you can then use it on your borders or wherever, rather than turning it in. You need to get a level surface with a fine tilth, and that can be difficult with lumps of turf getting scraped up by your rake.

Thanks for your advice.Last night I attempted to deturf by hand and found it quite a task when aiming to strip to min depth to save soil when moving grass.I have ordered a turf stripper today to complete over next few days.(approx 15 sq.m)I have also orederd rotovator to turn over remaining soil to de weed before adding new soil to make up new level.I will lay stripped turf on panels and degrass later to collect any decent soil attached.If all goes well,I estimate I can strip,rotovate,and make up levels fron topsoil stack in two weeks,allow one week final prep before bringing in turf.Thus laying in October.
Kildermore,It is only turf required,and my property is terraced either side by adjoining properties,while the rear is bounded by an old disused railway line with no access allowed,so access is zero in my case.thanks anyway.

I've got one more piece of advice - if you have any deeprooted weeds like docks or nettles, or any bindweed, ground elder, clover, dandelion, celandine, dig those out by hand first before using the rotavator - that will chop up the weed roots and distribute them everywhere, and each piece of root will produce a new plant...