Posted: 10/03/2017 at 15:14
Is the bad corner in the shade which way does the sun move around the garden and yes you will find modern builders compact the base with machinery never re-dig it lay the thinnest top soil on then turf. It usually ends up in time digging it all out laying drainage lifting the soil depth then laying a proper lawn.
For now, most lawns are very wet and you should keep off it until it dries out a bit that means any work will be done in around a months time or even later depending on which part of the UK you live. I would remove the turf from under the fence panels as it has no chance, I am assuming that is the damp corner, dig out a bit of the soil lay a membrane and use some sort of slate or pebble filling this will tidy up and help drain it a bit. Or you could start a border with some plants that will take some of the water up. You have all lawn and paving, the water has nowhere to go and the amount that has fallen this winter it is bound to be wet.
That is only emergency advice as any major work will depend on your finances and time to do the work, there is no quick fix, draining properly will mean removing large bits of the lawn and then re-laying again where would you drain it too? Borders are ideal and will take a lot of the water falling on the lawn, the plants or small fruit trees if that fence gets any sun will take up surplus water.
Sorry to tell it as it is any quick fixes will be just that and you will be doing it again next year, lawns take work as mine do and they were put down properly. Good luck.