shouldn't be a problem m8 as my cousin has done it in the past. Few tips for you on the information you need.
Is the laptop New, in this case it's not been registered,
it will just be telling them the asset tag on the base of the laptop and your details.
The seller can also do this on your behalf, then you can check online.
if it's 2nd hand the laptop is likely to be registered under the company/retailer or seller that had purchased it,
Dell will ask you for the name and address details of the original owner,
and then your details so that I could transfer it to over to you.
tips
1. Is it as described : brand new, unused, in original box with all original documents and cds.
(Ad says: This Notebook is unused and still in the original Dell box.
All software is still sealed and Windows remains unregistered)
2. How will warranty be transferred to you.
3. Who will transfer it.
4. What happens if any problems arise with transfer.
5. Is it already registered under their name and if so will it be a smooth transfer.
just be careful with ebay m8, and make sure the seller has a great feedback and isn't a first time seller as it could be a con.