My daughter had a flat head (plagiocephaly) from early on (2 weeks approx). She developed it due to a neck problem (torticollis) which meant she only used one side of her head to sleep on, and was likely due to the prolonged labour, and her being the wrong way round all that time.
Our GP gave us physio exercises to do with her at each nappy change, which improved the neck problem (though they were excruciating for us, as she screamed the whole time!). Unfortunately by that point, the damage to her head was already done. Her ears were mis-aligned by over an inch (if you viewed from above).
We did everything we could to minimise her lying down (sling, carried all the time, etc- which also helped with her reflux LOL) but even with repositioning, the head shape did not improve. Though she did sit unaided incredibly early, probably because of the practice.
She had a bulgy forehead, and one eye was smaller than the other due to the deformation (ok- she sounds like the elephant man- she was cute to us, but you could certainly tell something was amiss!). Her head was kind of trapezium shaped rather than an oval.
We went down the helmet route- Cranio, through Dr Blecher- and while it was heart-wrenching at the time I know we did the right thing for our daughter.
Our health visitor, and midwife dismissed me when I said there was an issue with her neck (even though she howled when I tried to gently turn her head). Thankfully our GP agreed with us, BUT did not take the flat head issue seriously.
I now see babies/children all the time with brachycephaly (flat across the back evenly) or plagio (flat to one side- wonky heads)- to some extent they can grow out of it, but not completely, and of course it depends on the severity of flatness in the first place.
Go to the MSN Group Plagio UK, read about people's treatment etc.
It is NOT cheap! It is not available on the NHS (seen as cosmetic, though orthodontic braces are just as cosmetic if you ask me, and about 50% of children get those, and dd would not have been able to wear spectacles had she needed them or a cycle helmet!).
It is a faff going to the appointments- nearest clinics to you are Leeds or London- especially when you're trying to minimise the amount of time in a carseat
It can also be very hard dealing with the stares, the sniggers, the pitying looks, the hastily looking away that you will get when you walk anywhere with your child wearing a helmet. All I can say is it certainly made me more aware of what parents who have a child with a permanent condition must go through on a daily basis, and my dd will be made aware at every opportunity that society today is diverse, and all the richer for it.
I know of another mum with similar problems for her ds, and they went down the CO route, but the results were not as dramatic. To be fair her ds wasn't as wonky, but you can certainly still see its not round. My dd has a lovely shaped head now- it will never be perfectly round, but no ones head actually is, and you would certainly never know she had had a problem.
Sorry about the length!