I don't think people on this thread have been exactly helpful OP!
This is the S&B board and OP asked for some ideas for holiday clothes for a British beach holiday as she's lost weight after having children and is feeling a bit rubbish about her wardrobe. I think the words 'Cornwall' & 'holiday' in a thread title are a bit triggering for some posters...
It's nice to get new clothes for a holiday and feel good about yourself, I'm sure OP isn't desperately trying to blend in with the locals, just wants to feel a nice beachy, relaxed vibe. Nowt wrong with that.
OP for British bech holidays I take a couple of pairs of Ralph Lauren chino shorts (navy and stone), some linen shorts from Cos, some long chinos that I wear rolled up, plain long and short sleeved ts in white and navy, a couple of racer back vests, a couple of nice thick hoodies from APC, a plain mid-blue linen shirt that I can wear over a vest top, straight led jeans that I wear rolled up, a stiped cream & navy cashmere sweater, some wide Legged navy linen trousers, and an oversize stripy shirt. Birkenstock arizonas in cream linen and navy suede, a pair of Arizona Love sandals and sturdy flipflops for the beach, trainers, a couple of fairly sturdy swimsuits for freezing cold seas, a linen throwover from Seafolly and a short terry robe from toast for the beach.
Obviously waterproofs!
That generally covers all eventualities, I don't bother with skirts or dresses, maybe pack one for the evening in case it's warm and you want to waft about a bit.
I hope that gives you some useful ideas.