repairing cracks in lawn

This is unusual - you don't say quite where you live, so if you're in the south, I can understand the cracks still being evident, we haven't had enough rain yet. Usually the cracks close up on their own once the ground is wet enough, so unless they're actual chasms of six inches or more, I'd be inclined to wait till spring and fill them in then if they've not recovered. Once I would have said fill with peat and sand, but the unavailability of peat makes that impossible, so I'd be inclined to use a decent, graded topsoil, bagged from the garden centre, or John Innes No. 1 if you want to reseed immediately, No. 2 if you don't. Remember not to use any kind of lawn fertiliser, or weed, feed and moss treatment if you want to do any reseeding.

You must take care with the mixture you use. Fill the cracks up to finger length with sharp sand. Use some of the soil in your garden (clay), mix 5 to 1 old compost and with care fill the cracks, firming in with a piece of wood. The grass on each side will grow over them. A richer mixture will give you green lines all over the lawn.

The cracks in my front lawn have gone since its been so wet but mine dont sound as big as yours? In the past when I have had deep cracks I have left the hose in them but that was not this time of year.