Too early to Roundup for lawn prep?

So my old thread (posted last October) is here: http://www.gardenerscorner.co.uk/forum/threads/my-garden-is-a-mess-is-it-too-late-to-fix-it.104797/

The garden was in a sorry state when we moved in. I chopped it down and left it over winter (see pictures below), and now I want to know (and perhaps I'm being too keen, considering the cold weather) whether I can start to prepare it for planting grass seed in the coming months.

Ideally (and feel free to tell me if this is completely unrealistic) we'd like to have something that isn't a muddy weed patch (and preferably resembles a lawn) by summer to have barbecues and the like!

I'd thought that in the next couple of weekends I could spray with roundup, and possibly dig it up in the weeks following, start sowing some seed say late April/early May and it will miraculously be luscious and green by say mid June?!?



Right now the garden looks like this (there is work to be done..):

 

A spring sowing will result in something vaguely resembling a lawn from a distance by mid June, but it won't be ready for barbecue parties.

You could maybe do it in sections, with a temporary paved area for the barbie this year and grass growing around it. Trouble with that idea though is getting it all to match nice and level when you lift the temporary paving and sow it with grass seed perhaps in time for the autumn sowing window.

 

Ahh, in reality there is quite a big patio area that would be adequate for bbq'ing - it's more about it just looking vaguely respectable... I assume it will need to be pretty thick and established before people can start walking on it.

So, is now a reasonable time to look at prepping it?

 

I would wait until it warms up a bit before applying the Roundup.

 

It is perfectly possible to dig the whole patch and remove every weed by hand.......not as difficult as it seems.

Then of course turf would be the quick fix and ready to walk on in two or three weeks, a good investment.
Trim the Ivy back also.