Most lenders offer the facility to borrow an additional balance to your mortgage at a later date to when you initially took out the mortgage. The reason that you would prefer to remain with your existing lender rather than remortgage elsewhere could be to avoid having to pay any early repayment charges. We can research the market for you to check that it is best advice to remain with your existing lender to borrow additional funds or whether to remortgage elsewhere to acquire a better rate.