Options to sort finances to exchange/complete as soon as possible

[avidteadrinker]

Would like some advice on the fastest option for us to complete on our family house purchase, its a bit of a long story so will try to explain as best I can

We decided we would reduce the mortgage on the family house we are purchasing by re-mortgaging on a BTL property I own to get a bit more cash out. This BTL property I brought prior to knowing my husband so is solely in my name at the moment. As we are using funds from sale of my husbands property to part fund the family house, we intended to put the rental into both our names to effectively merge our finances.
We applied for 2 mortgages (in joint names), one BTL and the other for the purchase, waited weeks for the mortgage interviews, then spent 4 hours in interviews with the mortgage company and asked specifically whether we could go ahead with the BTL in both names as my husband wasn't owner on the land registry. They said yes.
Now several weeks later, the conveyancer for the bank has come back and said that they require the BTL to be in both our names so will help us to manage that. However, research on the internet suggests that the land registry will need to be updated before they release the extra funds to us, which could take months
Plus the sellers of the family home are putting us under a lot of pressure to exchange/complete in the next month.

I've tried to call the bank today to get advice but they have been a bit useless. The options I see for us are:

1. Continue with the BTL in both names but it could significantly delay the purchase, putting it at risk
2. Do the BTL in just my name and transfer it to my husband later, but we may have to restart the mortgage process again because we 'applied online' (which we didn't) - the bank couldn't confirm if we needed to restart from scratch again.
3. Change the mortgage amount on the main house to increase it, thus not relying on the bTL funds, would probably have to restart the mortgage process again, and it would put us under more financial pressure on a month by month basis.

Both my husband and I want the path of least resistance which means we can complete as soon as possible, so my preference is 2.

But keen to hear others experiences or advice.

There will be stamp duty issue with regard to the transfer of ownership with a mortgage on the property if the mortgage is above £125k www.gov.uk/guidance/sdlt-transferring-ownership-of-land-or-property not sure if you’ve considered that? If there was no mortgage no stamp duty, if
Mortgage is below £125k no charge but if above there will be, be careful