A part built Solent just sold on eBay for £100 buyer to collect. I’m building one at the moment from plans bought on eBay (I’ve a build thread going as we speak). If you have reasonable building skills that could be an option?
Built ones are going for about £100 as in the post above, an unbuilt kit about the same price but yours may have some bits missing so, say about £75. As Dave M said the resto in Model Boats mag will drive up the price as people see how to do it. Hope this helps Mark