Hi Colin
Let me start off by saying that eyepieces are probably the cause of most disagreement on the big astronomy forums. They are very individual items, some people may love a particular eyepiece, while others hate it.
Zoom eyepieces, and specifically the Baader Hyperion zoom, do have a lot of fans. The main advantage of zoom eyepieces is that they provide a wide range of magnifications, all with the one eyepiece.
The main disadvantage is that, at lower magnifications, the field of view can be a bit small. With the individual Baader's the field of view is 68 degrees across all the range from the 21mm down to the 8mm. However, with the zoom, the field of view is, as far as I remember, in the high fifties/ low sixties somewhere for 21mm, going up to the full 68 degrees for the highest magnification at 8mm.
In the end, it is really down to individual choice.
I think a minimum field of view for a general eyepiece would be 60 degrees, although if you were to eventually buy a specific high power planetary eyepiece, you could maybe go to 50 degrees.
The new Skywatcher UWA eyepieces are a bit cheaper than the Baader's, and have had very good reports. I have seen through the 17mm, and it is excellent. Jimmy has just bought the 13mm, and I am looking forward to seeing through it. These are solid chunky pieces of glass, but I think your scope would be able to handle them ok.
www.firstlightoptics.com/skywatcher-eyepieces/sky-watcher-swa-70-eyepieces.htmlThere is plenty of choice out there, and, nowadays, it is almost impossible to buy an outright bad eyepiece. Apart from the Baader Hyperions and Skywatcher UWA's already mentioned, there are names like Speers Waler, Celestron Ultima, Explore Scientific (now difficult to get in the UK), William Optics, Meade (the 82 degree UWA eyepieces are superb) and if you feeling flush, Televue, Vixen and Pentax.
I would have to say that the individual Baader Hyperion's are very popular amongst the regular observers in the society, I think almost every one of us has the 17mm, an outstanding eyepiece.
One way to gather a good collection of eyepieces is to buy second-hand from UK astronomy buy and sell. Of the 5 or 6 regularly used eyepieces I own, all but one were bought second-hand. Remember that you do not need a large collection, 3 or 4, spread across a range of magnifications, is really all you need. Amateur astronomers tend to be very careful with their gear, and it is highly unlikely you will end up with a dud.
I would start with a good medium sized eyepiece, somewhere in the 14mm-17mm range, and then go from there. Ask yourself questions as you go along, do I need more magnification, lower magnification, a wider field of view etc etc. you can also use your current eyepieces to help answer questions, what is the best magnification for Jupiter, Saturn, the Orion nebula, and so on. What sort of thing do you particularly enjoy observing, widefield views of the Milky way, star clusters, planets etc etc.
Another things to consider is eye relief. How close do you prefer to put your eye to the eyepiece while observing? Do you have to wear glasses while observing? If you need to wear glasses, then a long eye relief is essential.
Your best bet would probably be to try and get along to one of our observing sessions, borrow a couple of eyepieces, and try them out in your scope. If you need any specific advice about a particular eyepiece, let me know.
Here is a link to the eyepiece page for Telescope house, have a good read at it to get some idea of what is out there
www.telescopehouse.com/acatalog/Telescope_House_Eyepieces.htm