Im going to take a guess here but those that have gone for 20s probably dont use it every day! It will be a complete nightmare, especially when combined with the Civics stiff suspension setup.
18s are the optimum for looks and comfort, the max should be 19 IMO. Even the you have a high chance of buckling the wheels with our UK roads.
A little tip, is you want the wheels to look big, get alloys where the spokes or the design stick out and not in. Those 20s in the pic dont look like 20s because the spokes go in, if you find 19s where the spokes go out, it may look biggerthen the 20s!
