If you want to buy a BTL the bank is unlikely to just do an equity release on your own home, they will want you to do a mortgage on the new BTL for max percentage whatever that is these days, used to be 80% for BTL, then you would usually do a top up on your own home for the balance if the amount was below top up levels or a full remortgage if amount was above what they could do as a top up.
However that was boom sort of stuff, I don't think banks do that anymore, it's basically 100% finance for a house.
Not sure they are going to let you borrow to put in a pension either, I doubt they would be in their reasons for borrowing list. Would it not be considered similar to borrowing to buy shares, that didn't work that well for banks/customers when they used to do that either.