Hi David,
there are two questions, firstly, what do you want it for? Trotting, ledgering, looking good?
Secondly, What's the budget?
A centrepin is for allowing a bait to move along the river at roughly the same speed as the current.....................or.................................being a Chris Yates "type" purist angler. Nothing wrong with that before you all start!
5 years ago, I didn't own a single centrepin. Now I have 15!
I VERY rarely use them for "barbel fishing".
Contrary to other peoples opinion, the "wallis cast" i find, is very difficult to master and a fixed spool reel is king for most of my dangling.
If you want to trot a float through though, nothing else comes close.
For trotting, my personal choice would be a Youngs Purist or Allcocks Match Aerial 4 1/5 inch. Superb line recovery and ultra smooth! Both reels are around £140-£180 for a good second hand one. I also have a 5 inch Adcock Stanton which spins forever (not always what you want) and has no ratchet.
For £ 80-£90 you can get an Okuma "Sheffield". Superb but a bit heavy. Again, spins forever (german engineering)!
If you want a ledgering reel, a Speedia or Trudex in good condition will be more than suffuicient but are smaller reels and therefore recover line more slowly. Personally, I find them a bit too small for big fish which are likely to take line.
As usual, it's all down to personal preference and I would definately recommend giving one a go.
I would recommend a good Speedia as my "all round" favourite starter, expect to pay £40-£50 for a good second hand one.
Good luck and enjoy.
Best regards,
Jeff