•Bad hosting prevents customers from finding you and may prevent your site from getting and staying fully indexed in the search engines.
•Some hosts will not let you change some of your site
•Some hosts configure incorrectly with the wrong clock time or sending DNS errors that prevent your site from being indexed. A server header checker can be used to ensure your clock time is not way off and your home page provides a 200 code and non existent pages provide a 404 error
•One can also use Web Bug or the Firefox Live HTTP Headers extensions to check HTTP headers.
Dedicated Vs Shared Hosting
Dedicated hosting is typically far more expensive when compared to share hosting. Shared hosting places many domain names on the same IP address & same server, whereas dedicated servers allow you to place just your stuff on a server. If you are going to make major investments into the web then it may be worth to buy a reliable dedicated server. As in shared hosting you have no security for your web site. In shared hosting there are chances of invading your web site by other spammers hosted on that same server but in the dedicated servers your web site is more secure as you have total access over the server.
Host in Your country
Getting regional focus in the search results can also be a better idea. Many major search engines give websites a relevancy boost if it hosted in the same location as the local search market. If you are promoting a site primarily geared toward Japan, it should not be hosted in UK.