Buying a domain name
You can buy a domain name from many places such as GoDaddy, NameCheap, Amazon Route 53, and even in CloudFlare, which is probably among the cheapest places to buy one, since there is no markup. Some of your considerations might involve the .com, or .co.uk, or .co and whether the name of your company is even available.
Creating a basic website
Depending on the type of website you need, you will have various options. If you are setting up the ecommerce element of your business and you are able to use cookie cutter webpages, then you can pick a template and get started on Shopify. There are many advantages of using a standard ecommerce web builder including some of the SEO widgets that are available as well as the ease of use and the standardisation that the user expects to see when navigating your site.
If you need your website for marketing reasons and lead generation for offline sales, then you'll want to use something like <a href="https://www.webflow.com/>Webflow, which provides you with a cloud-based website builder with the kind of functionality you expect from Adobe applications. Learning how to use software like this may involve many hours of work, so that may be a reason for you to get someone proficient in the software to build a website to your specifications.
Marketing & advertising your website
Once your website is hosted and setup, you will then need to go about trying to get 'traffic' to your site. It is the equivalent of footfall from the high street, otherwise you will not be able to generate much value. You will need to list your website with Google search, Bing, etc so the search engines can find it so your website can be found by people searching online.
One way of increasing the value of your website is to start creating content. People searching online tend to be looking for information, products, & services. Well if you have content about a certain topic, then it will get traffic from people searching for that topic. For example, if you offer cleaning services in Manchester, then you might create some topics in the local area where your service is available. That way someone searching for cleaning services in Manchester may come across your site. "How to remove red wine from the carpet" might be a topic you would explain to your site's visitors. And then, your visitor may see you offer cleaning services in the area and might then contact and buy your service.
Branch out your SEO
To get more online traffic, you will need to get a lot of online content referring back to your site. Think of these veins back to your site as 'backlinks'. These enable people on other sites to click on links that then go to your site. For example, if your company sells sodium-ion batteries, which are a much cheaper alternative to lithium ion batteries, then perhaps you could get your company reviewed in an electrical engineering website or magazine. This would mean people on those other sites would find your site, which simultaneously boosts your website's credibility in the eyes of the big search engines, such as Google.