Personally, I don't call up anybody unless they can offer a radar service.
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I find that most experienced pilots do exactly this - fly with a listening watch only
You are certainly a braver man than me. I guess when I get that experience I may do that, but the numbers of times that Farnborough have warned me of conflicting traffic that's helped me spot it
I'm also incredibly paranoid of infringing and in Farnborough's area (with heathrow and gatwick so close) it's nice to know there's somebody else watching what I'm doing.
Although, of course, you can't rely on FIS to keep you safe and in the right place. It's still down to you as PIC to maintain a good look out, and navigate accurately enough to avoid tea and biccies with the CAA people sans tea and biccies. It's just good to know it's an extra fail safe in place
