Query on Sale of Goods Act

Any advice appreciated!

I purchased a Sat-Nav, less than 6 months ago from an online retailer. The item was billed as **DAMAGED BOX** (i.e. the packaging was cosmetically damaged by a sticker). It then developed a fault (complete failure to power on) and the manufacturer advised that I could return it to them or to my retailer for repair/replacement. I decided to return to the retailer as they already had all my details to arrange the pickup etc. On receipt, they acknowledged the fault and placed a replacement order. They then emailed to say they were out of stock, then again to say the item had been discontinued and they would offer me a credit to my account. I phoned today and queried this and they agreed to contact the manufacturer, and subsequently confirmed that they had sourced a replacement and it would be dispatched by the end of the week. I then had a further email to say that because the item I had purchased was reduced because of the damaged box, I would have to pay the difference in price between what I paid originally and the 'new' price (approx. £20).I said I was prepared to receive the replacement in the damaged box of the original (in which the item was returned). They said that box had been destroyed.

I'm pretty sure that Sale of Goods act states the retailer must repair or replace in the first instance (without additional cost to me). The retailer has informed me that they can now source a replacement. Does this mean I can insist on a replacement at no additional charge, or can they just refund my original purchase amount? I obviously don't want a refund as I got the item at a reduced price and hence cannot replace the item on the open market without additional cost. My final bargaining point was to be that I would accept the original faulty item back and go direct to the manufacturer.

thanks in advance!

Update: Ebuyer still refuse to replace the satnav claiming that the SOGA does not apply as I bought a **BOX DAMAGED** item which was listed under one quick find code and that they could only replace with a new unit, which is listed under a different quick find code. They assert, therefore, that the two items are not like for like and that I have to pay the £20 difference. I've been round and round and they keep spouting the same nonsense that 'our terms and conditions say that we will replace like for like', but the EXACT same product is not like for like if it is listed under a different quick find code.

I then searched their website and found an 'ex-display' version of the same model in stock. It was listed as having the charging cable missing (I did not return the charging cable when I sent mine back for 'repair'). I asked them if this could actually be my unit and they said no and that my unit had been 'destroyed' when tested as faulty (I kid you not... Garmin, who emailed me about the fault, also tell me that it is fixed with a simple firmware update by them). I asked if I could actually be sent this unit and again the answer was that I'd have to pay the difference (£15). After 2 supervisors and 40 minutes on the phone, they finally offered to place the order at their cost price which meant I had to pay £1.70 to receive the replacement (!). I had lost the will to argue anymore and accepted the compromise.

If, however, when the unit arrives, it bears the same serial number as the unit I returned, then all hell will break loose. I'll update again when I get the delivery!

Update: new (to me) unit arrived. It *is* a different serial number to my original. On the plus side, although it cost me a couple of quid, the replacement did have a car charger cable in it. it was the USB cable that was missing. I can now put the car cable in my wife's car and leave one in mine. Was still going to write to Ebuyer stating that I think their policy does not adhere to the SOGA.