Stamp duty land tax and all normal purchase costs, such as valuation fees, conveyancing fees, local searches, are shared between you and the equity lenders. The fixed repayment mortgage lender does not benefit from any increase or decrease in the value of the property and therefore does not share the costs.
The costs are shared fairly between you and the equity lenders in the ratio of your equity funding. For example, iff your deposit funding is 5% and the equity lenders fund the remaining , you will share the costs in the ratio of 5/30. So if the total costs are £18,000 you will share £3,000 of the costs while equity lenders will share the remaining £15,000