Well done Neil, it's great to do something you really want to do rather than just a way of paying the mortgage.
Your database is by far the most valuable thing you have. If you invested in CleanersMate or similar and kept in touch with Clients, you will have a pure gold mine for someone. Work out average job price, no. of times per year repeat av. lifetime of customer, av referal value per client. Use this as a negotiating tool.
I can't see anyone buying your website unless they bought your business as well. Who would want a website with someone elses business name?
Sadly most carpet cleaners are one man bands with no system in place, no contracts in place, no maintenance plans, so 30years+ yields a second hand van and a few ebay bargains.