Gumtree/eBay decided in their infinite wisdom to remove the ability to create RSS feeds based on searches. I don't know their rationale for this decisions, however I notice that it occurred about the same time they implemented Search Email Alerts. One can only assume they want to be spamming us with emails instead of consuming via RSS.
Luckily for us/me, when they disabled the ability to create new RSS feeds they didn't remove RSS completely (i.e the s-feed.rss link). With some text replacement and some PHP, I've created this little script that converts the new search format into the old RSS feeds.
This tool was created for myself, but feel free to utilise it. If you have any comments/questions/feedback, feel free to contact me.