If you are paying $150 for an item, you will pay 20% VAT plus a 'handling charge of £8.
If the seller is happy to mark the item as a gift instead of merchandise or other, the charge will be significantly less as the first $60 is 'free'.
I would make a guess at around £36 all in on that figure.
Parcel Force are holding your package and they will be sending you a charge slip for you to pay the charges against your item. Just pay it online, very easy. They will then release your item for delivery
Please note that a Saturday delivery will cost you an extra £12 though