Advice from somebody currently job searching in the UK:
1. Post your jobs on LinkedIn and Glassdoor. Any other website is basically pointless (maybe HN's Who is Hiring? at the beginning of the month can get you some attention too) because people only search on these, and any other website is flooded only with job ads from consultancies and recruitment agencies so yours won't pop up.
2. Add your salary ranges in your job's description, otherwise you will get people that apply expecting more than you can offer and you waste both of yours time (I've been told this by companies during the interview, they wanted to make sure I saw the ranges and it fits with what I expect).
3. Replace your "take home challenge" with a "live coding session" (if you have one). This will attract older people that are married/have kids which usually can't set aside 4 hours during the evenings or weekends even if they wanted too, due to family responsibilities. This will show them you respect them, so you can spin it up as a "benefit" of applying. If you can detail the entire job interview process in the job post and how long it takes, then even better!
4. You're in Tewkesbury, engineers probably want to be in London, so let them know you offer a WeWork office in there too, if they need it. Otherwise your location is going to put off many people.
5. Make sure you actually answer when somebody sends you an email with an application, or questions. Many don't, be better than them. If you don't have an email address where people can send you questions then make one, or allow them to send you messages "InMail" on LinkedIn.
6. Please don't ask about previous salary, or personal details like sexual orientation or things like this during the interview process, like those creepy Greenhouse job application forms. I can't believe this is not illegal in the UK. If somebody at your company does this currently, tell them not to anymore.
That being said, if you had any jobs related to Ruby on Rails with a possibility to transition to Engineering Management in the next 1-2 years, I would have applied.