Well, good luck!
CD players in general need laser replacements every 10000hrs use...on average.
It really is a matter of if you think your machine is disposable @ 10000hrs or whether you want to fix it.
Pioneer laser assemblies for CDJ100, 500, 500 II and 500s (dunno if they are the same for 800 and 1000) cost a tad under £70 +VAT...But they come uncalibrated and need the Pioneer manual to set them up to!
Most service agents won't touch Pioneer because of their shitty supply of parts, extortionate cost and the fact that they won't accept returns (even if the part is faulty) from non-authorised spares centres or service agents!!
Compare that to almost any other pro-CD deck (Denon, Numark, Gemini, etc) where the laser comes calibrated, ready for assembly onto the board for around £35+VAT.
Add to that the fact that Pioneer spares take around a week minimum to come from Belgium (they keep zero spares stock in the UK) whereas most other manufacturers' parts are off-the-UK-shelf...
You can see why I say Pioneer are shite for service...
Technically Pioneer don't even service their own kit...they sub-contract to a company called SEME...who have the wonderful customer service attitude of: You didn't buy it from us, you're not a Pioneer agent so we won't deal with you"
Nice
As for your purchase, Kev:
Legally the retailer you paid for the goods is responsible for replacing or repairing the item should it be faulty under the warranty. After the warranty expires, though, there is a "grey area". The dealer might decline to service it, Pioneer UK might decline to supply parts as it was not purchased through them and Pioneer Europe could say it was sold outside of their territory and responsibility...thereby leaving you in the lurch! It isn't just Pioneer, to be fair, any company could say that. It is just in my experience a company such as Harman don't ask where it was purchased...they know a pro bit of kit is important to be serviceable and will do their utmost to fix it or provide the name of a contractor who will do the job on their behalf.
Knowing Pioneer, I would suspect that problems would appear...
If, like me, you paid £250 for a pair of decks in a flight case, then you would probably not care....If you paid £1500 for a pair of CDJ1000, then I'm sure it would become loads more important!