Okay a few suggestions here:
For a service business in Norwich, you'd usually want to reach people that are already looking for help. So in terms of online ads, I'd recommend you go with Google Search Ads instead of getting bogged down with social media. The reason being is that you're catching people right when they have a problem and are actively searching for a solution, rather than trying to interrupt them scrolling through Facebook.
You can target keywords like: "[your service] Norwich", "emergency [your service]", "[your service] company near me". Keep it focused on your local area.
In terms of what to expect for costs, it can vary quite a bit depending on how competitive your trade is. For some context, we're running a campaign for an HVAC company in a competitive area, and they are seeing costs of around $60/lead. We’ve also had a home cleaning company which got a cost of £5/lead. I'd usually suggest a starting ad spend of £1k-£2k a month to get enough data to see what works.
Make sure you enable the phone call extension in your ads so people can ring you straight from the search results. A lot of service work comes from direct calls.
Hope that helps!
