Had my rear ford focus suspension repaired.included in the invoice was part no 1487402 was i cheated?

I can't find that part on the web it is classed on the invoice as a link and cost 29.30 sterling

No and you got it cheaper it looks like.
http://www.amazon.co.uk/...B00CPJ02QG

Depends on what part you had replaced.

No, it is an anti roll bar kit, and is definitely part of the rear suspension on a Focus. Google the part number plus the words" Ford," "Focus", and "rear suspension parts" and you will see images of it. It comes right up on the search engines. The anti-roll bar (or sway bar) on a car makes the car so it does not pitch over on its side when it takes a corner. Kind of important.
As for the "was I cheated" part, it is highly doubtful that you were. The vast majority of mechanics face stiff competition, and cheating would be a death blow to their own employment. All that has to happen is for word to get out they were cheating, and boom, they are done.
Here's a few tips to assure you don't get cheated, even in a strange town with strange mechanics. First, do research. While you should not believe every online review, read them anyway. It gives a good idea of the quality of the shop. Second, find the shop that has been around the longest under the same owners. If they have been around ten years or more, it is probably because they are doing something right. Third, don't go with the lowest bidder. Shop around, but cross the way low guy right off your list. There's a reason he's cheaper than every one else, and its probably cuz he's cutting corners somewhere.remember, "cheap is dear". Last, watch your attitude. Businessmen are in business to make money by serving the public well. If you go in with an attitude of "You're going to rip me off", that attitude conveys over to the businessman. And guess what, buddy? You're a lot more likely to get ripped off.
One time I broke down in New Jersey. I needed a mechanic because all my tools were packed, and I just couldn't repair it on the side of the road. I drove into a garage I had never seen before, walked up to the owner, whom I had never met or heard anything about. The first words out of my mouth were, 'Wow, you have quite the operation here! I'm from out of state, and one of the locals recommended you. Said you do real quality work." That mechanic treated me like a king.
Oh, and one more thing. You will pay more for parts when your mechanic buys them than you would if you bought them yourself. This mark up on parts (usually 25%) is part of the mechanic's profit margin.You're not getting ripped off. Every mechanic world wide does it. It is part of the business model.