Fer, I may be totally wrong here, but I suspect that candid discussion of issues relating to longarm quilting is not easy in the UK. In comparison to the US we are a very small country and most longarm quilters here are using their machine to earn some money, so you are all competing in the same (limited) market. That might make an exchange of ideas and experience somewhat awkward.
I don't know how others feel, but getting something longarm quilted is expensive (though worth every penny, in my opinion). If I have a large bedquilt that I want to get finished, so an overall quilting pattern would be just fine, I may go to a longarm quilter who has a large range of pantogram patterns, and a computerized machine, so that the pattern I choose can be adjusted in size to be just right for my quilt.
If, on the other hand, I have a wallhanging, and I'm looking for quilting that's complex and artistic, but don't feel my own skills with a little old domestic machine are adequate, I would go to a longarm quilter who has a proven track record in producing some individual and visually stunning quilting.
It's probably very important to agree on all sorts of details about the quilting, write it all down, and have the customer sign it.
I hope that one of these days I'll produce a quilt top that'll be worth it to bring to you, Fer.
Lorchen