WTF!!

[Jeeqbit]

I would recommend getting the Complete edition because it gets all expansions up to the current one. Make sure it's for the correct platform. If the trial version is the PC version, expansions should be the PC version too and if the trial version is the Steam version, all expansions should be the Steam version too.

You should receive a code from the retailer by email which you can put into your mog station account (http://sqex.to/Msp) to register that you bought it.

You already have an account and the launcher because you have played the trial, so the launcher will download anything that needs downloading.

You can subscribe on the mog station as well http://sqex.to/Msp

[Tagros]

I had problems trying to sub as well; the mog station just wouldn't accept my postcode. I double and triple checked I was typing it in correctly, went back to my letters from the bank/utility companies/council, yup, definitely the correct postcode. I had bought the expansions but was soon going to be locked out from playing it because I couldn't sub...
This is the first site I can ever remember being on - and I'm a software engineer - that won't accept spaces in your postcode without giving you the information that this is the format you have to use or mini fields to enter the postcode correctly (and then behind the scenes the mog station could reformat it as required). It was so simple that it never occurred to me until I got an email from the help desk a week later saying this could be the issue, and it was -- guessing they've had more than a few moans from the UK about this.
After that it was easy and just used the steam wallet to pay for the sub.