Thanks a lot for your reply Gidders!
I really do love my D40 (though a D90 is my current dream camera, if I had the money!) and really wasn't sure about selling it and going back to a bridge camera. It's just as I said, I feel pretty limited due to only having the 18-55 and 75-240 lenses, also this lens is only manual focus due to the D40 having no internal motor.
I am thinking of selling just the 75-240 and seeing if I can do what you suggested and get either a close up filter or extension tubes. Think I will have to forget the wide angle for a while though.
My friend says that if I marketed my photos properly, I could probably sell some and make enough money to buy all the lenses I needed...Nice thought!
Thanks again!