Double room in modern Harpenden flat

I am looking for a lodger for the second bedroom in my flat in Harpenden. I would like to share with someone clean, tidy, quiet and respectful. The room currently has a single bed but it could fit a small double (or regular double at a push). I am a young professional who likes to be active and healthy so someone with a similar mindset would be great. I would prefer a Monday to Friday lodger or someone who is not always home. I would prefer not to share with someone who works from home.