I’d be amazed if they can certify the design of the doorset, based on what you say. I can see how this is going to run:
1. They’ll bombard you with any technical information vaguely relevant that they can download off the internet to try & convince you it’s OK; or
2. They’ll tell you “we’ve been fitting these for (x) years & there has never been a problem before...”; or
3. They’ll tell you “we’ve fitted these at (premises name) & there wasn’t a problem...”; or
4. They’ll not come up with any convincing technical evidence at all & will look glum.
If they can’t certify them, there’s nothing to stop them shelling out & getting the design tested at one of the Lab’s (Chiltern Fire at High Wycombe, BRE in Watford, the Building Test Centre at East Leake or Warrington Fire). Alternatively, give one of Lab’s fire testing dept’s a call & see if they know anyone who’s successfully tested sliding doorsets, & give the supplier’s name to the contractor, so that they can replace the doorsets?