The GB boys presence isn't that great for a J5 - all five British lads left in at the QF stage are age 16 or 17, which is pretty old for a J5 - but it's nice that they all get a chance to play proper competitive tennis and gives a chance for the better ones to build on something, maybe boost their ranking for their college applications etc.
The girls is a lot stronger in that way - in the QFs, Isabella Walker is only 13; Aimee Knowles is 14, as is Georgiana Mititelu, and Shamiso Ndoro. So that's four of the six GB girls left age 14 or under
I've seen 3 of the 4 girls mentioned( not seen Shamiso). Isabelle Walker is the best of the bunch, but has had some tough draws in domestic ITFs and should be ranked higher.
In the boys a couple are Scottish based and haven't travelled to much, but are good players.