Gilts can sometimes be a couple of days early so check her to see if she's getting milky.
We use a farrowing arc, in other words it came with the bars. I've never used a lamp - as I've never farrowed when it's been that cold, I would if I did though. I sit out in the arc with a torch & towel off the piglets - though I don't like to interfere too much, it's reassuring for both of us ( I think anyhow), to be there. When mums restless I wait outside 'till she settles.
Also we've found putting a temporary barrier ( a plank of wood usually) across the front of the arc will stop any piglets falling out accidently and getting cold.
Mum may humph 'cos it may rub against her udders as she goes in & out, though.
By the time the piglets can scramble or jump over it they are able to find their way home & not get lost - or so we find.
In our recent litter we had one piglet that jumped over it on all fours - like it had little springs in it's legs
I love farrowing time enjoy