You are lucky that you have got the co-operation received up to now. Try one.com, they are even nastier ...
I have written about the way these sort of companies work before. The sales model is Germanic / Scandinavian in origin, the T&C are given to you when you sign up, you accepted them when you paid. You didn't read them, nobody reads them ... you assumed they were reasonable, this is a reputable company, right? They are English, they have an office in London you can ring for help - or are they American, they have an office in Chicago you can ring for help?
These hosts are not cheap - their prices are affordable, for one or two domains, their reliability re. downtime is reassuringly good, they have 24/7 telephone support. Everything radiates quality, security and stability. In fact, stability is the key word - but for the hosting company.
You agree to work their way when you sign up, you are allocated disk space and bandwidth accordingly. What happens after that depends on how "vicious but legal" their T&C are, and whether you have already bought your domain elsewhere.
Will they provide hosting for an existing domain - or will they ask you to transfer the domain to their registrar account? Some, eg Bluehost, will let you point an existing domain at their servers. Other than that, if you take up a domain with them or they get their paws on your domain, that domain becomes untransferable. If it is a UK domain you might over-ride that by using the Nominet transfer mechanism, but, even then, it might not be possible.
I had a "free" domain registered to a "free hosting" site generously provided by Micro$ht to promote their Live site builder software. "My" domain? No, it was registered in the name of Melbourne IT - pull out of the free deal and everything was theirs. They dropped it eventually when I did nothing for 2 years, so I caught it later.
You are allocated enough space to host 15 domains easily, but you can only add more domains if you upgrade your package.
Once you've worked that out, you are likely to find their "easy site builder" keeps dropping out on you, losing work and unexpectedly locking up. That's because it only works with IE6 and above, it is in the T&C, didn't you read that? That's why the support team couldn't work out what you were doing wrong ...
If you put up a large site that occupies the space in a way that encourages visitors, you will probably want to upgrade because you are getting penalised every month for exceeding your bandwidth ...
You want to transfer ownership of the site? You built it with their site builder, they own it - the T&C say so. You can't move it or transfer it, that's their template and anything you put on there becomes their property. You have an exclusive licence to use it for you own purposes. Anybody else wants to use their services, they are free to set up an account and rebuild a similar site. But not on "your" domain - all you can do is keep it going, or drop it (and they want 3 months notice if you want to "close your account"). If you do drop your domain, you won't be able to catch it, because they will continue your registration for another year (still in your name). If you complain about that, they will ask you for money to reactivate your account, and worse.
If you try to pass an account over to someone else, they will dump on the purchaser as soon as he tries to pay a bill with a card registered to a "different" person etc. and they will not allow you to redirect the domain to someone else's hosting. The only way around their T&C is if you buy everything with a prepay card that you can pass on to a purchaser, and that only lasts until the card expires.
They have plenty of satisfied customers because those customers are happy with the service provided, and no inclination to do anything but use one site for their own web presence. Those sort of people don't want to make web money, they just want a presence with the least effort.
In the UK or US, if a situation arises where you have a problem with which a company cannot help you, the staff usually try to point you in directions which might be useful. In most of Europe, it is standard practice to say "no" and stop there. After years of experience, I have found ways to get around the average "bolshie jobsworth" in a face to face situation, but these foreign registrars - very hard work. It wouldn't be so bad if they didn't own so much of the industry under pseudonyms that look "local".
Go dig around Moniker and Snapnames, the parent company is registered in Switzerland, they are owned by Germans, their UK "tag" is Schlund, they own 1&1.
Like Nissan make cars in Durham, like Honda make cars in Swindon (because their Indonesian plants got flooded in the last monsoon).
As well as that, if the domain host "goes down", the domains get farmed out to other registrars and the site can be live inside a week. If the site host "goes down" you can get alternative hosting, redirect the domain and be back into action in a couple of days. If both site and domain are hosted in the same place, that is a mess. No backup, and you are without sensible resort ...