Layers to keep me warm

[AdelicaArundel]

Yes I know, I know- it's still August, and too early to think about it; forgive me S&B peeps.

I am approaching 50, underachieve thyroid so prone to feeling cold. Work about 50% from home, Lots of research reading, written or typing work. So a large part of my working day is spent sitting still at a desk. I have to stay warm or I find it hard to think- and it takes ages for me to heat up again once I'm cold.
It's fine this time of year. But I will be miserable from November through to April. That's while wearing (usually) M&S Heatgen layer, merino or cashmere jumper over, Berghaus or North Face fleece over that. Feet in Ugg type slippers or wool socks and boots. While the house is not particularly cold, I don't put on heating all day just for me. Room is usually 17degrees or so.

Occasionally, I need to pop out to visit clients, so my layers must be reasonably smart or have the option of being easily swopped for neatness.

So, what I would like to ask, is, if any of you have ultra warm layer recommendations. I've been looking at the Icebreaker merino layers for instance but don't know if it's worth the investment?
Or there may be other, better options that I don't know of?
I've seen people on here recommend putting a fleecy dressing gown over everything... are there better/warmer varieties of fleece?

Many thanks for any advice oh stylish ones!

Ooh mumobsessed, you've prompted me to veer off the dressing-gown course onto onsies.
Next have a rather nice looking all-in-one, fleece with a hood. Very tempted (may have to prised out of it!)

Claire, I will buy a gilet in any case, I think. They are so useful- my last one was a down version, bought in sales about 8?years ago. DD1 has taken it . I think I might get a Kingsland one which will properly defeat any drafts. I've been eyeing a nice bronze coloured one.

Keeping baby warm is a worry- DS was an autumn baby.
At Christmas, in my parents house, he was very grizzly (almost 3 months, very cold old house) and my mother advised me to follow her trick.
She wrapped a warm (not hot at all) hot-water bottle with a towel, and laid it at the end of the cot. Not touching DS but the radiant heat was enough that he stopped complaining and went to sleep.