TUBULAR HEATER - ADVICE NEEDED ASAP !

[nature child]

Hi folks, I'm new here ! About to have my ~ Lean to greenhouse fitted to the side of my property, and, I must confess , I know pretty much next to nothing about growing things in greenhouses ! So, no doubt I will need to ~ Lean, ( significant word ! ) on you guys regularly for support ! My odd jobs guy will be coming to fit the greenhouse in just a few days, ( hence my hurry for the info ) and I don't yet, have a heater for it. Prob is, not sure, which size / wattage heater ( I want one of those ~Tubular ones ) is best.

The Lean to is 4ft X 2ft will be fixed to a South / South East facing wall, the surrounding area is ~ Vast, wide open fields and mountains, so VERY exposed to the elements here. ( winters are ferocious ! ) I was hoping to purchase a 2ft 80watt, tubular heater. I've found what seems to be a nice, reasonably priced one on Ebay.
Will this heater be ok ? Will order one just as ~Soon, as you guys give the go ahead, Many thanx !

[Dillbert]

there's so many un-specified items of your post . . .

4 ft x 2 ft - this is essentially a "window box" type thing?

if you live in the tropics, no heat is required.
if you live in Antarctica, you'll need a lot more heat.

but 80 watts of heating is not going to work in any temperate climate. if you get frost in your area, you're gonna need a bigger boat heater.

[nature child]

Hi Dilbert, Many thanx for your speedy reply Well, I live in the U.K, Rural Wales,high up on a
mountain. The Lean to will be attached to the patio ( faces South ) against the wall of the
house, ( East side) Not yet sure what seedlings I'll be growing there yet...... I spoke,yesterday
with someone who gives advice at an online garden centre, where they sell this type of greenhouse.
I gave him all the specs, of my location, He stated, quite categorically, that a 2ft 80watt heater
would be more than ample, for that size of greenhouse. Me, well I'm just newbie " piggy in the middle "
not knowing which way to turn !