Roses

So, is it a "sickness" or because the previous rose has depleted the soil of goodness?

I agree with that in fact I did just that using a large cardboard box filled with fresh soil.....and used micro wotsit. Before hand I watered the hole with Armatillox. It worked

Cherry we agree on most things, except maybe TV presenters ;D
As I love Roses and don't have enough space I have had to replace roses in the same place. I've done it several times and that's why I understand the problem.
A rose will not flourish where another rose has been especially if it was old. My first attempts were all failures but now I take the problem seriously and tend to be OTT when it comes to replacing the soil. It's folly to try and take a short cut as it takes a long time to know the outcome which WILL be a waste of time.
I dig out the old rose and remove an enormous amount of soil down two spits at least. Water the hole with Armatillox. after a couple of days I plant the new rose with soil from somewhere where there has been no roses or use fresh Tree/Rose compost.
As I said earlier, I still suspect that there's something in the soil that unless totally removed, ruins your new rose.
To give you an example, My Sister's friend replanted an entire rose bed, a big one. They all failed. I asked him did he replace the soil. He said yes but only around the roots. He has now planted other plants.

You have more faith than us we wandered along the rows of roses at the GS, We sniffed a few that were the right colour but smelt of nothing, smelt some heavenly ones which were the wrong colour, we didn't like the ones with loads of little flowers or the ones with huge blousy flowers and the others were just green so we bought a fern

One day I'll find one we love AND will suit our ground AND which Cherry will approve of for quality and strength.

No no! You must plant to suit your own tastes and you have to work out strength, etc., yourself. I am not an expert. We are doing this together. I make mistakes. I really mean that.

I am most impressed with Merlin's planting actually. I have known about this system for two years and have never mentioned it before in case you all thought I was mad, but Merlin has used it and it worked.

Sweetpea and I have favourites and it is an old Bourbon rose called Zephirine Drouhin. In your area it may get blackspot, but there won't be much better. It is too windy for blackspot here, so fungal diseases don't take a hold. It takes two or three or more years before it starts to climb, but it should climb and is worth the wait. No thorns, gorgeous too.