I fish bamboo 100% of the time in freshwater, and I do agree totally with what everybody else have said about the fact that you should cast the rod before buying it. I say "should" since this is not an ideal world, and you will end up, sometimes, having to buy a rod on "faith".
I do not own any rods from contemporary U.K. makers, but the ones mentioned above have great reputations and I'm sure you won't go wrong getting a bespoke rod from any one of them.
I do, though, own a few rods from contemporary U.S. makers, and many more that would be considered "vintage", with ages ranging from 40 to 90 years. Contemporary U.S. makers I would recommend from experience are Dennis Stone and Tim Zietak. These two make very high quality rods at an affordable price ($900-$1200) and are very approachable and accommodating.
Steve is right in saying that new rods from contemporary makers have actions that go from parabolic to fast. Additionally, production values are consistently high, with excellent bamboo quality and first-class fittings.
I must add that many, many "vintage" rods will also cover the same range of casting actions.
Allow me to take a "production" rod-maker as an example. Orvis. Orvis still makes bamboo rods, all of them impregnated, rather than varnished. The new rods are very nice aesthetically with a crisp medium-fast casting action, but are perhaps somewhat over-priced. Vintage Orvis rods, on the other hand, are IMHO the best value in bamboo.
Orvis made a huge number of rods over their 175 year history, and some of their rods are considered real classics among bamboo rod lovers, e.g., the Orvis Flea 6-1/2' 4wt at 2oz, or their various Battenkill models from 7' to 8-1/2'. They made rods to suit a myriad of casting actions -- I have a 6-1/2' 3/2 2-7/8oz Rocky Mountain Special that would be fast by any consideration (this is the rod I hand to my graphite-wielding friends when they scoff at my "slow" bamboo rods. Their eyes invariably widen when they try it out), and the aforementioned Flea is just a lovely, lovely medium-slow rod that requires no effort to place the fly where you want it. Since all Orvis rods, except for models before the mid-1940s, are impregnated, they're practically water-proof from the get-go and endure better the careless angler.
So what is "best value"? For example, an 7-1/2' 2/2 3-3/8oz Orvis Battenkill from the 1960s or 1970s in excellent condition can be bought from reputable dealers for $650-750. If you settle for a single tip section, there are bargains galore. The Orvis 99 2/1 7' 3-1/2oz, for example, a nice medium-fast 4wt, can be found for $400-500.
And that's just Orvis. Then there are the other blue-collar classics like Granger, Heddon, Phillipson, etc. Blue-collar only because they don't command the premium, staggering prices of a Payne, Garrison, Gillum or Dickerson. But wonderful rods in their own right.
From the U.K., Sharpes rods are amazing value and great casting rods, though a little heavy. Their impregnation process comes from Orvis, and they made blanks for both Orvis (the Equinox range) and Leonard (the Duracane range). Many of the tapers, especially in the Fario range, come from Pezon and Michel, and these would be considered properly parabolic, staggered ferrules and all. And then there's Hardy. The 7' Marvel. The 7-1/2' C.C. de France. Amazing rods where form and function find the perfect fit.
I apologize for an over-long post. You can probably tell by now that I love bamboo rods. If you haven't already done so, you might want to browse the Classic Rod Forum, where bamboo reigns supreme, and where many bamboo rod-makers from all over the world hang out. You will get to see great examples of their work, and if you wish, ask any number of questions. Answers are always forthcoming.
One thing about bamboo rods: you need to use the "considered" cast, where you wait to feel the rod loading on the back-cast, and feel it load you will, which I must say is really satisfying. Coming from graphite you might, in the beginning, produce power too quickly on the forward cast (tailing loops galore, and I speak from experience

!), but because bamboo rods transmit so much "feeling" it doesn't take much to adjust to their rhythms.
Finally, and this is no small consideration, compared to graphite rods, bamboo rods tend to hold their value over a longer period of time, with some of them actually increasing in price.
All the best and welcome to the slippery slope,
Kenneth