hello huub, the very first question in this matter is whether the additional services (wrapping + etc) is "per product" or "per whole order"
if this is per order, opc could be the right place to add it, but remember that customers do not really like too large checkouts and they might get scared of it.
so if you planned to do this per product, there is also another solution - VM Product Bundles where you could create those service products (like wraps, etc..) and have it redisagned within the product details themselves.
my OPC supports also rendering various modules inside OPC checkout section so maybe if you could have a module that would show a styled list of services with add to cart button it could do the job as well - these can be either shown as own product lines in the cart/checkout or as a summary line within OPC checkout.
best regards, stan