My dd is 13 and wears Jack Wills. She loves it and she has had lots of their stuff. She is a size 6/8 (tall and willowy, so the perfect size for the range) and it is all true to size, imo. I would go larger on a jumper, as dd does. In terms of washing, she had a red cable knit sweater last year which was stunning and still looks the same now. We tend to wash on a wool cycle in the washing machine, spin it extra at the end, then dry it on the wet room floor overnight. The under-floor heating is a godsend for drying things flat.
She's had coloured polo shirts and they do eventually fade out a little on the collar, but the colours are usually dark to start with, so more prone to do so.
Their shirts are divine. They wash beautifully and iron like a dream. She also has their jeans, which are a lovely skinny fit and they wash really well, hold their shape and their colour well (and we're talking black and dark red jeans here).
If you get chance, put your name down for the Jack Wills outlet store. You have to put your details on a waiting list and be invited to join (marketing tosh, but it works to some degree as some people don't have the patience) and you can access stuff at reduced prices throughout the year. It's the main place I buy from to be honest.
I've never noticed glaring staff to be honest and I've been in a number of times as a size 18, tall woman who can't buy anything! Also, at Christmas, they were handing out free hard boiled sweets and they let DD have loads to take home with her, offered to gift wrap her purchases for free and were generally lovely (this was in London, though we usually shop in York). I do like Jack Wills. Much better than Hollister imo.