Yes you need to pay VAT on NBT. NBT is not something that you are bound to collect from your customer (unlike VAT).
You need to pay VAT on everything you charge from customer as a general rule. You may collect NBT from customer which will be decided by the bargaining power of you & your customer. However if you just add 2% on the price, it will not get you the full NBT you are liable to pay. That means you will have to pay 2% on 102. If you want to recover full NBT (with the cascading effect) you need to charge 2/98 from the customer.