Hi
I've found that the more local you keep the links the more relevant they become, irrelevant of .com or .co.uk
If a .com domain who uses keywords of say, London Car dealers, and your website is (for example) London Car Parts, then the domain suffix becomes less significant. The link's relevance becomes higher because they are directly related.
If your keywords are London Car Parts, and you get a link from Shanghai Carpet fitters .com then both sets of criteria become irrelevant.
That's what I've found in my experience. Others may have another slant on this.
