When I first started collecting I tried with Limited success to find the UK Tamla Motown 500-599, 600-699 etc
As Pete says you will pay a lot more for certain UK Titles.
I soon turned my attention to the US.
You can always find something of Interest.
I have found a lot of pleasure picking up the USA singles from Various different Pressing Plants Including the DEMOs for each.
Many USA can be quite Rare now for certain DEMOs and Stock Copies, especially when looking for a particular pressing plant.
Even these can still be found at an affordable price if you are lucky.