Thanks both, very useful. I think I'll opt for clear out/tidy up initially and see what/when we use it most for. The back triangle I eventually can visualise being split between play area then some adult space at peak of triangle patch. Ive an idea for a triangular pergola as it catches the last of the sun. Rechargable lawnmower...Ive never heard of the likes!! Googling now...
Just mow and clear to start with, give yourself a few months to work out from real experience what you are going to use the garden for, who is going to use it, how much you like gardening and what you've already got. By the end of the summer you may want to pave the whole thing over, or turn it into a jungle full of exotic tender plants, or devote it to organic veg, or it will have become a ravished bare patch of a children's playground of its own accord.
When you clear the beds of their weeds make sure you dig the weeds out properly and then if it's all bare and horrid nip to the garden centre and get some summer bedding to cheer it up a bit - that's all those petunias and geraniums and bizzie lizzies and things in multipacks. Or get some veg - courgettes are great as they fill lots of space and you only need a couple. Or you can often get cheap plants and herbs at farmers markets and so forth.
If you need to buy a lawnmower and it's quite a small space I can heartily recommend the bosch rechargable battery ones - brilliant mowing without a cable in an awkward space.
You need to think about which way the garden faces and perhaps test your soil acidity (you can buy a little kit or see what sort of things grow well in neighbours' gardens) to figure out what will grow there. Otherwise you could buy a lot of things that won't grow. Is it very dry? Are there loads of slugs? I think if you get armed with that information first you can make plans for planting. Look at www.crocus.com (or something similar) for planting ideas but better to buy in a garden centre where you see what you are getting and don't pay postage for everything which can be huge from crocus.com
No idea where to start! Its fairly large and in 3 separate sections...one to front of house, relatively square, one to side, rectangle and likely to be devoted to off street parking. And rear...we're corner house so goes down to a point, long triangle shape. All currently turfed, some nice but overgrown borders. Im guessing a goid clear out and mow/strim is best place to start...but then what?!