I've just checked on a few (fairly random) schools.
The school I used to teach at (many moons ago, in Sheffield) starts work experience on 2nd July, for a fortnight.
The school that's now local to me start their work experience on 9th July, for a week.
Another nearby school start their work experience on 16th July, for a week.
The school I attended myself (in the days when we had pet dinosaurs) also start their work experience on 16th July, for a week.
A completely random school in Birmingham also has work experience, for one week, from 16th July.
So it looks like July is now the favoured month in many areas.