Adding dead fish or fish food is not a particularly good way of adding ammonia, true, these will eventually give off ammonia but there is no way you will know how much ammonia you are adding.
As per the Cycling A Tank article it states
"If at any time you test and ammonia is under .75 ppm and nitrite is clearly over 2 ppm, it is time to add more ammonia. Add the same full amount as you did the first time."
The full amount being 3ppm, how are you going to know from using fish food is going to give exactly 3ppm? You simply cannot, at least not without testing many times.
A much easier solution is to get a bottle of ammonia as the previous posts have said, Kleenoff, Dr Tim's One and Only Ammonium Chloride etc all can be bought online for a few pounds.
Homebase hardware shop do still sell a household cleaner with ammonia, its an own brand, white bottle with blue lid if remember correctly and only about £2.50 or something like that. However, have heard these are becoming scarce to find now.
Or you can go via eBay and buy this bottle or similar, I used this one and is good ammonia, at 35% strength so be careful with dosages using the calculator as Typhoon221 linked to.
Using any of the above suggestions of ammonia, this is by far, the best and easiest way of adding ammonia to your cycling tank.
Absolutely no excuse for using fish food when there are products of ammonia you can easily get access to buying since you are UK based.
(NZ & AUS have difficulty getting ammonia due to strict importing laws)
As for measuring tools for dosages, there are quite a few things you can get, again easiest via online website and you can get the most commonly used methods which tends to be droppers and syringes.
I personally used a 1ml syringe which i bought from ebay for literally pennies. I keep this syringe just purely for ammonia. There are various sized syringes up to 5ml would be the biggest I'd suggest for ammonia dosages, whatever you feel best with really.
Fishless cycling typically takes between 4 to 8 weeks. Mine took about 5 weeks in all, very satisfying way of doing a cycle compared to doing hard work with daily water changes with fish in cycles which is pretty stressful for both keeper and fishes.
By the way, if you have not already got one, you will need a test kit for testing ph, ammonia, nitrite and for later nitrates, a must have item for beginners.
Recommend API Freshwater Master Test Kit, can be bought from most chain LFS for between £25 to £35.
Online is cheaper, got mine from eBay for £17.99 if remember right.
Good luck and keep us posted
i am about to purchase my first tank and have been reading the site and decided to do a fishless cycle. my question regarding this is about ammonia; does anyone know of any highstreet shops i can purchase this from? also is there a tool you use to apply the ammonia e.g a dripper? is there also a way to calculate how much ammonia needs to be added and when in relation to the tank size? thanks in anticipation people 
