We're sortof doing this.
The garden we've moved into is horrendously overgrown as the lady moved out a year before we bought the house and has enormous flower beds, One flower bed alone is 15 metres long and about 3 meters wide in places. The gardener who we have used to look after the garden for the last lady, he was here 4 mornings a week for her and still couldn't keep on top of it. We are ripping out everything and turfing, but i'm doing it bed by bed.
Gardener is doing the bulk of digging out and levelling, im redistributing plants, kept some but most are going to neighbours and the really scrappy ones are going to the tip, the shrubs are too big to be dug out and relocated so they are being chopped down.
I pay our gardener on average £200 a month (£10 an hour) and have done that since April, I'd say we've another month of digging - so end of september...so labour is £1,200
Turf....so far erm....about £300 (we could seed but have a puppy who loves to dig and do zoomies, it wouldn't survive!!)
I'm adding weed matting and gravel to lots of areas, the side paths, patio area, around the pond etc so that's another £300 on gravel
Then, of course, there's plants we do want to go in (large palm tree, row of photinia trees), we'd like a pergola and outdoor lighting, a raised bed along the front (there's a dip between roadside verge and our garden so I need sleepers to have a clear edge to our lawn plus fencing all around.
I am making do with the patio, paths and existing hard landscaping and working my design in around
We've about another £7k to spend. so I think we'll be on about £9k by the time we've done everything.
I did look at getting a landscape gardener in and he wanted £3k just for the designs - im sure i'll make mistakes along the way which a professional wouldn't but im enjoying going at my pace. Im taking all the rubbish to the tip, about 3 runs a week (and I've a ford ranger so can fit 3 builders ton bags in the back) so that saves on a skip.
If the garden is really bad perhaps get someone in to clear and dig over, put turf down so it's manageable and presentable then build your garden up slowly?
Thinking if your garden is 40ft that's what 12 metres? Assuming 12 metres square and turf at £4.5 a metre (it ranges here between £3.50-£5) that's about £650 in turf