Was just talking about Granitethorpe on facebook the other day. Not been over for ages which is daft living reasonably close by. Cant comment on whether its overgrown, however getting in may be harder than it used to be as there have been a couple of new housing estates crop up near by and its now been properly fenced off. There is however a public footpath that runs round one end so nothing to stop you having a nosey, in fact I may well take a run over there at some point and have a look