OK, different viewpoints.
In my experience, whether you are paying 10 pounds or many times that, then downtime of the server still means your website is unavailable, long-term relationship or not! (and can be the result of a digger breaking a fibre connection, before you come back and say that cheaper hosting is more likely to be down - whole data centres are sometimes 'unavailable' for hours in the event of a fibre problem).
I used a UK based hosting firm for some 10 years until recently when my annual hosting cost doubled (without warning during the previous months) because of a takeover.
They still run with the same name, but instead of having servers in Canada, USA and UK - which allowed me to have an account on a USA server to host more domains for the same cost a UK-based account (with a quarter the number of domains allowed).
I had used US and UK servers for clients to provide extra mail servers, which few hosting firms offer (unfortunately) and the hosting firm decided (without warning) to stop using USA and Canadian data centres, and didn't think to tell customers.
I understand that when a firm is "on the market" their users are the last to know, because part of the sale price depends on X,000 customers, but I assume the closure was after the takeover.
I'm just giving that example as a "long-term relationship" may count for nothing. I didn't use that firm exclusively, so had alternative hosting accounts and could cancel when I found they had decided to stop their cheaper US-based hosting options.
Not sure that spending more is much of a guarantee of better or more reliable service, and these days, with firms going bust, I would hesitate at any (high) annual payments in advance, because they could have vanished in 3 months, even if they have been going for 5+ years.
For anyone new to hosting, there's a recommendation that 2 mail servers are used, and for reliability, they should be on different parts of the internet. Most hosting services offer shared hosting for your domain, and only the one mail server.
For my clients, I've always used hosting from different companies so even if one has planned maintenance (sometimes at night in the USA so early in our day in the UK) then the other server will handle incoming mail.
If e-mail is really important, then they would have a mail server at their office, but in case there is a problem (eg power cut/ problems with internet link/ dead mail server), there's still at least one backup server on the internet from one of the hosting services I use (and costing a lot more than a pound a month, since I'm charging a client a moderate fee for this server (under 30 year though, given it may never be needed).