Andy i had this exact dilemma and opted for the Nikon D40 though less pixels (entry level dslr).
Correct me if im wrong but if you go for the D60 you will be limited on lenses as they are afs.If you decide to go for the Nikon,make sure you save those few pounds and go for a VR lens.
Though you can go for prime lenses with the Nikon D60 everything will have to been done in manual,this will restrict you some what.
The kit lenses are very good on the Nikon,i have the 18mm-70mm and 70mm-200mm but have tried the VR....and they are better by a mile.
In saying this,the Nikon D60 is an upgrade of the D40 and if the results of the D40 are anything to go by from an amateur like me....the D60 will take some beating for the money.
Some shots with the D40 click here and im always playing with the settings rightly or wrongly lol :-))