But I get the impression that these things are a lot more anal in the UK
Not really, the examiner wants to know you can divert OK and give a rough estimate on time - does not matter if it is a bit out as long as you adjust it, so if you have worked thumb lengths as 6 mins and they fly as 5 then adjust your eta accordingly and you should be OK, a lot of people do make it harder than it needs to be though.
