These guitars were top end at the time of their production from the late eighties to late nineties and there is interest in these guitars from both players and collectors, they are often for sale on ebay and seem to fetch anywhere between 400 and 700+ pounds depending on condition, colour, the presence of "case candy" or original documentation, exact model and obviously the number of interested bidders.
If a seller is upfront about changes and mods it is unlikely that they are trying to con you.
The interchangeable nature of fender guitar parts and the readily available supply of aftermarket and used bits make it sometimes difficult to spot a "wrong un". I am mentioning a couple of my pet hates that are frequently seen on these guitars offered for sale.
Firstly if you are a collector and buying a particular guitar as an investment then please beware if you are paying 200 quid more than what you can get a good playing guitar for just because it has its original documentation then make sure it is correct. There are plenty of guitars out there from the eighties and nineties being sold with the original fender owners manual, might be original but it may not be original to that guitar i.e. they are surplus owners packs from new models. How can a guitar from 1989 have an owners manual that was printed in 2002? This is true of all the various "case candy". The paperwork changed over the years just like the guitars so if you are looking for that do your homework. Believe me there are a lot of old guitars with new documentation. Might be original fender but original to that guitar is very questionable. Why not? You can pick up a set of the latest edition case candy for about 2USD and it might add 150 to the value of your guitar if some sucker doesn't do their homework. The actual manuals from the eighties and nineties (at least three different designs) are a lot rarer and rarely come up for sale separate to guitars they have the date of patent of design printed on them somewhere and it should approximate about a year either side to the date of the guitar.
The Lace Sensors fitted on Strat pluses are readily available as aftermarket parts but the wording on them is different, often the word fender is ommitted. Also early Lace Sensors (87-around 92) had the wording printed on the top of the flat surface of the pickup. This proved to wear away quickly with regular play so the design was changed around 92 with a recessed print to protect the wording from pickwear. Again you may see the more modern pickups or aftermarket ones dropped into a earlier Strat Plus which should ring alarm bells as to the guitars authenticity.
The roller nut mechanism has also had three incarnations, very early ones had a kind of slanted split between the thick and thin strings. From around 88/89 another variation was used until around 93/94 when the last and thinnest nut was used.
The position and nature of the headstock logo also changed so again do your homework, the later models (96ish on) have the serial number on the back of the headstock.
If you are thinking of buying a strat plus there are a number of useful resources on the net. If you have the opportunity talk to the buyer before bidding and arrange a viewing to try it out. Do this before bidding as on collection is too late to change your mind. The fact that someone is offering collection suggests they are confident that you will be pleased with what you get ad they have described it honestly.
Most honest sellers will gladly discuss the pros and cons and arrange a viewing. If someone wants you to spend 600 quid based on a single photo and the answers to your questions are evasive, indirect or even abusive alarm bells should ring. Responses like "this guitar is obviously not for you" suggest there is something to hide.
I like these guitars and am all up for people changing their guitar to their own personal tastes. Good ones are still a great buy for less than you can buy a new US strat. But beware there some sellers knowingly or innocently cashing in on the popularity of this guitar as a players guitar and as a collectors piece.