Returns costs - how much do i give?

[inspirefuture2014]

I have been asked by a buyer for a return.  They originally collected from me (postage was an option also but they wanted the goods quickly).  Now they have decided that they wish to return the goods, they are also asking for us to pay them the cost of the fuel they used to collect the goods.  Am I obliged to do this.  I am happy to follow ebay policy and pay the return postage and then refund them but am i obliged to pay fuel costs from collection.

Thanks

This pertains to the birth pool I sold them.  When i bought it i inflated it, deflated it and then packed it up.  They said there was a puncture, however the puncture looks like a tear which absolutely wasn't there.  I'm not sure if they did it when they were setting it up.  Anyway they contacted me and I agreed to give them a partial refund of £35 as they would then have to repair it.  they  repaired it and then sent another email saying that one of the air valves was defective - which it wasn't when i set it up.  Now they have asked for a full refund and refund of costs incurred while collecting. 

I have a feeling that I am being taken for a ride on this and that it has been there intention since buying (they tried to negotiate a low best offer very early on in the process and then decided to pay the £115 I was asking for...)  There was a lot of to-ing and fro-ing going on.  

However in the interest of being a good ebay seller (which I'm fairly new to) I want to try and achieve the best resolution. Not sure if I am being strung along though....

Thanks for your help so far.

Oh and they paid paypal.

I made the refund via the original paypal transaction. Thanks

So to be clear - they have instigated a return through eBay.  Can ebay follow through with it even though they collected in person and had the opportunity to inspect?  Or has this the potential to lead to Ebay stepping in and resolving in his favour?  I'm ultimately trying to protect my Ebay position as I  know that a negative outcome will affect my ability to buy and sell in future...  Thanks for all your advice so far!

[*vyolla*]

How did you make the partial refund? Did you refund it from the original transaction?