proof of employment being a issue

hi guys,
wondering if anyone knows how to deal with this matter. I applied for a mortgage (Halifax) just shy of 6 weeks ago the most off the time is sorting out employment,
as I'm on maternity leave they didn't require me to send them p60 just wage slips and letter of employer guaranteeing job title and hours on when I return.

now they wrote to my manager to ask for some details, so he answered them and sent it off, he got the same letter again, so again answered questions and sent it off.

I emailed Halifax to find out what was going on and they said the reason they sent letter back is due to this reason,
I work as part of a franchisee of a large company, I had put down my franchisee name as my employer as this is who it says is employer on p60, though my manager wrote saying it was the company, now they said they need to confirm that we are a franchisee part of a company (if that makes sense)

I have contacted Halifax twice via emails asking if they would like my p60 as it shows on that who my employer is but on the front also has the company name so would hopefully clarify this. though still not heard anything, my manager is getting very wound up and says he will send it too head office next time (don't blame him). which I know will delay things even further than they already had. the seller wanted a quick sale and everything apart from this was sorted in first week including valuation.

so does anyone know any other way I may be able to prove my employment is a franchisee part of a company or is this something out of my control?

thankyou

xxxx