Stephen,
Yes, they are reasonably good, if you don't mind the fact that they're not exactly true to the books (although hardly any adaptations are these days!) I have the set and they are enjoyable, but as you can imagine they have tinkered around with the stories a bit! (I wonder what Forester himself would have thought

)
Since this series was made for television and 'family' viewing, it seems that some of the stories have been altered or added to, to maintain some sort of continuity for those who don't know the books. This has involved stretching historical reality in many of them and in some cases goes a bit, er, 'overboard.' However in other areas this seems to work quite well. Without giving too much away, I hope, I am particularly thinking here of the men of Hornblower's division, whom he meets in the first episode, The Even Chance, and then remains with throughout the series. This of course would not have strictly happened in reality and the men would normally have been dispersed to other ships following any commission, save perhaps when an officer had achieved a certain rank and men would have followed him. However this ploy does allow you to get to know them and watch both their progress and that of Hornblower and his (or Ioan Gruffud's) relations with them. (This also allows for a certain amount of humour, which in many respects I think the books lack.)
I thought that that was a good idea on the film maker's part and actually fills out the character of Hornblower himself. Presumably too it was thought that the Hornblower, as depicted by Forester in the books, was rather one-sided in that few other characters were allowed to develop, saving perhaps Bush, and I have thought that myself. Here however, other characters are allowed the limelight and I thought that a plus. There are also quite a few well-known actors in the series, beside Gruffud, such as Robert Lindsey, who I thought made a convincing Pellew (and who in many scenes actually steals the show), and Cheri Lungi who played the Duchess of Wharfdale. On the other side of the coin, some of the episodes almost reach a point of being ridiculous - and I am thinking here particularly of the mutiny on board the Renown, where Hornblower is of course one of the junior lieutenants.
I will say no more, except to say that I think that the series was well made on a small budget, and couldn't have been expected to be on a par with Master and Commander. I think you will enjoy them – if you can accept the faults. You have actually prompted me to watch them again!