Hello Samantha, welcome to the GMB.
Both Sue and Roy have given valid points - from different perspectives. Sue is constantly developing her interest in paperweights (:thup:) and Roy is a legend amongst collectors of Ysart (and also a few Whitefriars!!) weights :sun:.
My own view about your weight is that the defects (the white on one petal and also the split cane at the top of the central element) are distracting but it is the sort of weight that gives many collectors the chance to have a signed Paul Ysart weight without paying the full (and often very high) cost of a perfect example.
As far as I am aware it was generally true that Paul Ysart would not release something that he felt was substandard. However, I have seen several of his weights that have some form of defect but for which he clearly did not feel the need to destroy it. In purely statistical terms, yes, a poor Paul Ysart weight is rare.
When it comes to pricing for resale of Paul Ysart items, both perfect and flawed, this is difficult to comment on for many reasons. In this instance, you will need to trust the buyers (eBay or regular auction house) and allow the weight to find its own price. You could set a reserve that you feel could be reasonable and see if it sells or not. If it does not, then lower the reserve and try again. I would expect your weight to make more than £200 but how much more would be up to those interested in it.
Examples of many Paul Ysart weights, with the actual sale prices can be viewed in the Past Sales section of Selman Auctions (US-based outlet): http://selman.com/pwauction/cat_past.html
Click on any link in that page then search for “ysart” within each auction. A close match to your weight (but with the py cane in the design rather than in the base) is Summer 2007, Lot 98. This sold for $800 hammer price. A flawed example was in Spring 2008, Lot 172 where the ground is poorly finished, and yet it still sold for $750 (after failing to sell in a previous auction).