Welcome to ChefTalk!
I'm going to have to give a disclaimer. Since you are in Manchester, England and I am in the USA, I can only guess as to what stones are available. I have been looking at the sites you list above, as well as Amazon.uk.
One disturbing feature I am seeing is that many of the stones are 175 mm in length. You need the stones to be at least 200 mm long by 50 mm wide.
Your budget is 70 pounds. Does that include VAT?
If you haven't done so already, I would suggest you read Chad Ward's sharpening tutorial which is on egullet: http://forums.egullet.org/topic/26036-knife-maintenance-and-sharpening/
It gives a lot of information about sharpening in general. Mr. Ward also wrote an excellent primer on kitchen knives and sharpening, An Edge In The Kitchen, published in 2006. I don't know if it's available in the UK (generally, for American readers, I suggest they find it at a local public library or through a library interloan program, but whether that will also work in the UK is something I don't know).
My condolences on your having a Henckels 4-Star chef's knife. The steel in those knives is either identical to or akin to X50CrMoV15 steel (also known as 4116 steel) and is usually heat treated to be tough. Unfortunately, that makes the steel quite a bit more difficult to bring to a sharp edge.
The Eden Ceramic Sharpening Rod is in general a good idea. Knives such as the Henckels 4-Star can use a honing rod (the proper term for the rod - it really shouldn't be the primary sharpener) in between sharpening sessions. However, the web description leaves out many of the details which are needed. First, what is the length of the rod (excluding the handle)? The length should be at least as long as the blade it is honing. Second, what grit is the rod? Ideally, it should be as fine as possible.
Going the water stone route may be your best process. As I mentioned above, you need a stone at least 200 mm by 50 mm. With your Henckels, you probably will need a 1000 (1K) grit stone to bring it to general sharpness. However, you are probably limited in the degree of polish that the edge will hold to about 5K maximum. You can get and use stones with grit higher than that, but 4116 steel generally won't hold polish above that level for long.
As for stropping, I'm going to get a little bit lazy here - if only because the amount of detail I wrote this last November covers the subject. The thread is http://www.cheftalk.com/t/82913/stropping and my posts begin at No. 10. As for stropping compounds, you might need to check to see what's available in lapidary supply firms.
Hope that helps