A very stressful experience.
We had 2 issues with Marwona...
The first issue is returning a damaged 800w stone from Spain via their free return labels using Correos (Correos have a maximum weight and size limit and the 800w stone plus packaging exceeded both these limitations) and having to navigate the return using taxis at a cost of €40 - bear in mind the 800w is a huge and heavy box. Ultimately Marwona did arrange a UPS doorstep collection - which is what they should have done in the first place. They disbelieved us about the weight - I had to send them photographic evidence, and they moaned about how much is was going to cost them to arrange the collection. This is not good customer relations.
The second issue we had was because we had to pay back the original €44 shipping costs when we returned 2 x 500w stones plus their respective stands because one was chipped and both gave off an indescribable noxious odour. So our original outlay was minus €44. We also had to absorb the cost of another taxi which cost us €10. (All was good with Correos this time as the 500w stones are smaller and lighter).
I believe the onus is on the seller to absorb all costs for the return of damaged/faulty items.