My baby is 7 weeks old and has recently starting wriggling in her bassinet when sleeping and is moving to either a diagonal or almost horizontal position sometimes with her head pressed up against the mesh sides of bassinet. She wears an arms up TOG to sleep. Is it okay that she wriggles like this or should we be doing something about it?

Many babies do wriggle & squirm & can be quite active.
Its not necessarily about stopping this but ensuring the environment remains safe.
Sometimes it is because they like hands free to touch their face or suck on fingers.
Try baby with arms out of the swaddle suit you are using.

Are you using any bedding (sheets or blankets) in bassinet?
You could try moving your baby to a cot with more space.

Your baby may soon be attempting to roll.
Most babies are rolling from 4-5 mths - some earlier, some later.
https://rednose.org.au/article/what-do-we-do-now-that-a-baby-has-started-to-roll-over

How does your baby go with tummy time when awake?