Hi Gooner67,
I've spoken to various members of the team today who have been remarkably helpful in making sure I give you accurate information. At the moment the smog levels are listed as 133 in London and Beijing is 69 so for today at least it is worse here in the UK.
When we send tours out to China there are a number of things that our Duty Office monitor including smog levels. During your trip, if at any time there is a need to wear a mask, the Tour Manager will advise the group. There is no need to purchase a face mask before you leave the UK, these can be purchased while you are away and I understand that they are available to buy in most shops. One of the people I spoke with informed me that in the 8 years he's worked at the company, we have only once advised a group to wear masks.
I hope this information helps,
Kindest regards,
Julia