Just follow the instructions in the IRS link found in the FAQ for getting a tax id via phone from outside the US:
If you find it too difficult, use an Aggregator. The FAQ has a link to a list of them.
Your statement about needing an SSN is not correct.
Apple allow free use of their software to all. They stipulate that any book created using iBA must be free.
You cannot ask for money for any book. Donations is a payment and therefore you would be infringing Apples TOC of use.
You cannot have any eBooks made using iBA on a website for payment or donations.
You can sell only on the iBookstore and you can submit free books.
I doubt any book in review will be accepted if it contains requests for donations or payments of any sort.
Apple deal strictly with any infringers accounts are cancelled and a life ban imposed.
Opening a paid book account and getting an EIN numbers is very easy if the applicant gathers the correct information.
The information about donations is incorrect and could cause you real problems if you go down that path.
You do not need a US social security number.
I suggest you first open your iTunes Connect ..if you don't have one...then get one ASAP.
Check out the Banking and Contracts section. You can walk through the documents and check what you need to do..then close them.
You will need an EIN number, best way is to phone the US direct, it takes about 10 -15 minutes and you get the number there and then. As you are in the UK, you will need an IBAN number from your bank. It deals with Apple needing to pay any money from do.d books i to your account from the USA.
The EIN application form can be downloaded, print it off and fill in the boxes. When you phone the US, have this form with you. It saves time and they ask you for info by the box numbers.
Get a cheap phonecard giving reduced cost calls to the USA.
Next go to the iBook Author discussions and search EIN.