My "old" Mate Chris has an older Spark 15 at Shanklin sailing club on the Isle of wight.
What can you do Steve ? she is an old gal over 30 something now.
Old discoloured boats are easy to spray with a light coat of Halfords car paint the same colour so no primer. this is so the thick paint wont chip off in use. top up if needed and can wash off with Acetone.