Wholeheartedly agree with all the above, BUT, if you want to do it at Norwich, you must book in advance otherwise there is a very good chance you'll get thrown away and if you do decide to land anyway you wont get the training discount. I don't know where JohnT got his info' regarding "not much traffic" from, but (in common with many other places), they often are fully booked 2 -3 days in advance for ILS training, and
despite the high traffic levels will do their very best to accomodate you even if they are landing on the opposite runway - a bit exciting, but it works a treat.
Justin Beaver, it totally irresponsible to do an ILS to a military airfield when it is closed, even if you do broadcast your intentions, bear in mind that the airfield may be activated at any time for arrivals and departures which usually will only use the UHF frequencies, and neither atc nor the aeroplanes will moniter the VHF.