We're pretty fortunate in England in having a fairly stable supply in most areas compared to some countries. For many years, the statutory standard has allowed a 6% variation from the nominal 240V.
Certainly in my area it's only on very rare occasions such as during storm conditions that I've seen it drop below the minimum limit, and I don't think I've ever seen it exceed the maximum. I think once I registered about 252V, but most of the time I never see higher than about 245V absolute maximum.
