Lemon tree question again !

lacmarshall_sO6YKT_

recently I got a lemon tree , only small ( 12”max) 
As it is small this year I have choices where I can over winter it 
1- green house , can keep temp around 3c in deepest winter 
2- south-east bathroom window , never ultra warm in there and humid 
3- south west lounge window , warmest room in house with rads and gas fire in winter and a lot of sun when it shines 
4 unheated north facing outhouse with plastic roof not much full sun but light room 
where do you think it would appreciate it most ? 

When bigger i guess it won’t have so many choices , either green house or outhouse 

Borderline

I would choose 1 first and 4 as second choice. Both should be fine. The key is to keep the roots protected. You can do that by wrapping bubble wrap around the outside of the pot.

Obelixx

For winter, as much natural light as possible as it'll be in flower and fruiting form most years as it matures.  As @Bordeline says you can protect the roots with layers of bubble wrap around the pot and you can add a layer of fleece over the foliage at night if it's forecast to get very cold..

lacmarshall_sO6YKT_

Thank you both for the quick answers 
sounds like the green house then with the canna Lillies 

Cheers