I have some bad news for you - you'll probably never feel completely settled in either country. At least, this has been my experience. I have now moved between the US and UK on the following occasions:
1) Moved over in December 2002
2) Moved back to USA in December 2003 - only stayed 3 months as British (now ex) husband broke down in tears one day and told me he did not want to be there
3) Moved back to UK - March 2004
4) Moved back to USA - May 2006 - this was after ex-husband decided that yes we would have a better life in USA and that we really should make a 'go' of it - I moved over first so as not to sacrifice our savings and find a job. Found said job in 2 months and the week before the ex was supposed to move over, he told me over the phone that he wasn't coming and wanted a divorce
5) Moved back to UK - August 2007 - this time I moved to Scotland upon divorce (ex was a lawyer so was able to make me out to be a monster and get an expedited divorce!) being final as I missed the 'European' way of life including holiday entitlement
6) Moved back to USA - April 2009 - accepted a contract working in Miami and partied for the whole time
7) Moved back to UK - January 2010 - and I've been here since. Met my current husband in the same month. I have been having yearnings to return to the USA for about a year now!!!!
What I've found through all of this is that I mainly want to move back to the US when the weather is at its worst here - i.e. Jan/Feb. This year however has been horrendous with rain all throughout the 'summer'. Once I am back in the US however and have some sunshine, I start to miss the idyllic and cozy way of life afforded by long, cold and dark nights with candles and hot tea. Or never needing a fan or A/C in Scotland or seeing hardly any bugs or any snakes!!! I also start to detest the over commercialised nature of everything in the USA...the broadcasters shouting on TV, the work culture of always having to be switched on and chained to the company 24/7, etc etc etc.
I've decided before moving again, I'll explore buying a holiday flat in Spain, France or Portugal
Good luck and you are definitely not alone!