Its your expectation that you will be able to eradicate, and then remain free of, black spot which is erroneous. Black spot is endemic - you can only ever hope to control it rather than get rid of it. Spray with a good systemic fungicide regularly, according to the instructions, and clear away dead leaves, as you are currently doing. Good pruning helps, effecting a more open shape to the bush and allowing extra air flow between branches. Feeding with a specialist rose feed helps increase resilience and resistance, but ultimately, some roses are just very susceptible to black spot and, like the poor, it's always with us...

For all you need to know read the section on roses on this

http://www.armillatox.com/

I was going to suggest a sulphur soil treatment, but that's what armillatox is, isn't it, Scrumpygraham?

Oh yea, I'd forgotten about the sulphur soil, Gattina, and it was me discovered it! The heat got to me yesterday, made several booboos, I even bought the wrong plants and had to take them back to swap them today.
Tiger 123, check out thegreengardener website - they do something called sulphur chips or sulphur soil, and also a wettable sulphur you can use as a spray. The sulphur soil is spread beneath the roses. Said to work well - the only reason we have so much trouble with blackspot now is because of the Clean Air Act, which meant we're now not breathing in sulphur particles all the time. But it did keep blackspot at bay...

I think it was you that put me onto it in the first place, Bloomer - for the first time since we moved here, we have no sign whatsoever of blackspot on what were previously disaster cases!

Erm, bamboo actually...

Oh Gosh, Bamboo - I'm having a few senior moments this evening - I'm so sorry! Please forgive me. I'm trying to write this without my glasses, too, 'cos I've put them somewhere safe and now I can't find them. 8-(

Thanks to you all! I will certainly follow up all of your advice. Just noted that some recent growth is free from this problem. I fed the rose in spring with Top-rose and have once a week given it a feed with a very famous soluble plant feed. I only water in the mornings and never at night. It has now started flowering with no signs on the petals. The sulphur soil sounds like my best bet.