Thanks, I don't mind using long exposures, I have a tripod.
I think I'll go for one of the R72 filters, the 950nm ones are a little expensive for my liking!
Believe it or not I ordered a 10 stop filter yesterday, cost me all of £2! Info in this thread: http://www.talkphotography.co.uk/forums/showthread.php?t=151141I think you may be wasting your cash. Spend it on a 10 stop ND instead; much more fun (if you don't have one). I have a D40 and the in camera IR filter was so strong using the Hoya R72 was pointless (i have subsequently sold it). Even with flipping channels as per 'Brads IR action' or manually playing with the end product resulted in shots that were nowhere near as good as I had seen/expected. I tried long exposures too, again ... think you would be better off buying an old Nikon D50 as they are superb for IR work. I would do a search for 'Hoya R72' or 'IR' on Flickr by camera model; that will give you an idea of what is achievable.
Having seen the instructions on the 'Net for converting a D50 (you need a replacement filter to protect the sensor), the D70 will be easier to do, only because the two welds on the D50 are screws on the D70 (I took mine apart when neither my insurers or replacement providers wanted my old knackered one (after I dropped it)).