I think my skincare regime is hopeless. Basically a standard face wash and Clarins moisturiser - active? Day and night cream.
OK, so you need a better routine, more on that below. 
I exfoliate once a week using a ESPA polish. Your body, yes? Not your face 
I don't work out enough - I used to last 6 months stopped and putting weight on.
Could you fit in 20 mins of yoga a day? You could do it in your garden if you have one, and with your DC. I've done yoga with my DC since toddler-hood, there are some great mum + tot routines on YouTube
. Plus its a great habit for your DC to grow up with.
I eat too much sugar.
If you supe up the rest of your nutrition it will be easier to reduce the sugar as you'll have more energy anyway. I didn't find cutting out sugar completely made any difference, but I don't have much anyway and my nutrition is otherwise pretty good. Plus I like the occasional cake and I'm all for everything in moderation.
I'm low on Vit D and Iron but I supplement. There's a free app called "Chronometer" which measures your daily intake of vitamins, minerals, carbs, protein etc. Its a bit of a faff to set up, but very easy once you get going and helps you be much more aware, I find, of trying to balance your diet without supplements. Or at least improving your nutrition overall 
I don't supplement omegas. Ground flaxseeds have made an enormous difference to me, they have to be ground so that your body can absorb them properly, but they're tasty and cheap too. I add them to everything now. A good balanced omega supplement (make sure its balanced 3, 6 and 9) should make a huge difference to hour skin and how you feel quite rapidly.
I need to look into retinoids
The Ordinary do some good, cheap ones which are a nice starting point.
What is an ideal skincare regime - should I seek out pro facials?
No, I don't think pro facials are much cop tbh, once you know what works for your skin, which takes a bit of trial and error, and a bit of knowledge of ingredients, you can do it yourself much more effectively.
Basic skincare AM -
Double cleanse (I use natural African Black Mud soap), toner (something not harsh, I use rosewater), facial oil, hyaluronic acid, facial moisturiser, sunscreen. Then makeup if you wear it.
PM routine -
Double cleanse, toner (glycolic acid), facial oil, hyaluronic acid, facial moisturiser, occlusive layer (I use Vaseline).
I have found that the skincare powerhouses are:
retinoids/retin-A
glycolic acid (The Ordinary and The Inkey List do good, cheap ones). If you're starting a retinoid or retin-A, cut this out until your skin has properly adjusted to the retinoid.
hyaluronic acid. Very, very moisturising, but needs to go on a wet face, so after you've applied facial oil or moisturiser as it pulls moisture into your skin, and it can't do that if there isn't any moisture to pull.
facial oil. Some say it should go after your facial moisturiser, but my derm is very pro it going before, and before does work better for me.
occlusive, this locks everything in and makes it all work more effectively. I use a thin layer of plain old Vaseline, some use Nivea blue pot, or Weleda Skin Food. Both of those break me out though, so I stick to Vaseline.
sunscreen. I use Canmake Mermaid Gel (cheap on Amazon) as its non drying and non greasy, but Biroee Watery Essence is also excellent. Asian brand sunscreens are light years ahead of most Western ones in terms of consistency and quality.