I'd wait another month yet Pammie

If your greenhouse is heated and you can keep the temps up then my suggestion would be to start a couple off now and wait, perhaps, two weeks and do some more. Then carry on until you have enough. If the early ones don't survive then you will only be two weeks behind with your next lot!
My greenhouse is not heated so I won't bother until the end of march at least. Which ever way you go then good luck with them!

Heat alone is not enough. I've found that tomatoes started early on under heat never make much progress and become etiolated even in a clean greenhouse.
Seeds sown much later often make robust plants which overtake those sown earlier.
So definitely wait another month,as Moon grower suggests.
(Peppers and aubergines ARE worth starting earlier though.)

I usually set mine off in mid march during the easter holidays. plenty of time yet. :o)

I agree end of march and even then when they leave the propagator it is sometimes difficult if we have bad weather to give them good growing conditions

I have planted tomato seeds at the end of January to mid february before now in my greenhouse , yes i do have a heater in there.
The people that have bought my tomato plants of me have also said how sweet and juicy they are as well.
Ive already sown my tomato seeds .This was done 3 - 4 days ago