Extending the Tier 4 and reentry after it has expired

[svevenstar]

Hi! I'm currently enrolled in an American university and was just accepted to study abroad in England this fall. I plan to also stay for the spring, but my university here in the US will not approve me for another semester of study abroad. My plan was to acquire a Tier 4 visa for my fall term courses so I could extend it if needed, reapply to study to my English university for the spring term, declare a personal leave from my college, and continue studying in England. My question: can I extend my Tier 4 visa if I'm a student at a UK university but I'm not a registered student with my home university (so the courses I take in the spring will not contribute to the acquirement of a degree back home)?

Also, I plan on travelling throughout Europe during the winter break. If I end up not staying for the spring and therefore have a Tier 4 visa for courses that last for fewer than six months, I know that I can only stay in the UK for seven days after my classes end. When can I reenter the UK? Will I be able to reenter on a tourist visa within a few weeks after the expiration of my Tier 4 visa? So long as I have proof that I'll be heading home soon (e.g. a flight plan)?

Thank you so, so much for your help!