Ammonia is better than fish food because you know exactly how much ammonia you are adding. With fish food, it had to break down and you have no way of knowing how much ammonia is made, therefore no way of knowing if there are enough bacteria to support a sensibly stocked tank of fish.
I found Jeyes Kleen Off Household Ammonia in my local independent DIY shop; if you have one near you, see what they stock. Failing that, try Ebay or Amazon. The Jeyes ammonia is 9.5% - it doesn't say on the bottle so I emailed them to ask. You need the % to work out how much to use, see Calculator in the Useful Links in the side menu.
Some brands of bottled bacteria do contain a small amount of ammonia, and looking at your results it's possible the one you used does. But probably not enough to grow enough bacteria. The bacteria will only multiply till there are enough of them to deal the the ammonia present in the water. Their numbers are controlled by their available food.
You don't have to start again. If the bottled bacteria does work, it'll make the cycle much shorter. But not do it instantly. Adding ammonia will make sure that when you do get fish, there are enough bacteria to remove all the ammonia they make, and the nitrite made from that ammonia.
And once the cycle is complete, you can add most of the fish on your wish list straight away.
I've just had a quick look at water parameters in Leighton Buzzard. it seems you have very hard water, which is great for guppies and other hard water fish. The centre of Leighton Buzzard has hardness 333 ppm or 18.9 dH. You can check your exact figure by entering your postcode here
http://waterquality.anglianwater.com/map.aspx But this does mean that you won't be able to keep soft water fish such as tetras without altering your tap water.
