Intended date of travel question.

My wife and I are intending to move to the UK by February/March 2018.
We're planning 8 months in advance to reduce any headache (including getting our beloved dog over!).

I see the UK Visa form currently only lets us select up to 17th December 2017 as our intended travel date.
If we choose 17th December and visa is granted, will we have to leave for the UK by end of 17th December? Or do we have a couple of months to play with?

My wife and I are intending to move to the UK by February/March 2018.
We're planning 8 months in advance to reduce any headache (including getting our beloved dog over!).

I see the UK Visa form currently only lets us select up to 17th December 2017 as our intended travel date.
If we choose 17th December and visa is granted, will we have to leave for the UK by end of 17th December? Or do we have a couple of months to play with?

Your intended travel date can't be more than 3 months ahead of the date of your online application so it's too soon to be applying yet. It's great to start your research early though. 

If you want to travel March 1st 2018 for example, the earliest you could apply would be December 1st.
The vignette (visa sticker in your passport) is supposed to be made valid from your nominated date or if that has passed, the date it is granted, it is only valid for 30 days so you need to enter the UK within that period. It's really tricky logistically.

Lately, for those lucky enough to receive their visas prior to their requested travel date, the visa is made valid one week earlier, sliding the 30 day entry window forward.

Unfortunately there is no guarantee that the visa will be received before the date you want to travel.  With priority processing, you should be okay.  And hopefully they will honor your requested travel dates (there was a period of about six months where they were not).  It's tough!!

Certainly is tough!

My wife and I met through mutual interests online - completely out of the blue and neither of us looking at the time.
Our governments push for more of us to be online and globally connected but don't make it very easy if you happen to fall in love.

Thanks for your help guys. I'm sure I'll be asking more in the coming months!