Use an agent my friend. Simple and hassle free. Keep your wedge in your high interest account at home. No probs with good reputable agents. Make sure you have a trusted UK address for obvious financial reasons. Good luck.
Use an agent. Its not a straightforward process when you do it for the first time. I'm by no means unintelligent but I found it quite daunting. Agent took all the stress away and it was all done in one day. 3 month extension, 12 month extension, 15 months in all, bank account opened, ATM card, still using today and agent supplied the
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0thb. A stress free pleasant day. Good luck in whichever rote you choose.