I hope you don't mind my answering a question posed to someone else. Hopefully it's helpful.
My DD got an offer from LUS two years ago. For exam preparation, she did sample papers from Latymer Upper and Manchester Grammar School which we'd heard were very similar papers. She also practiced with sample papers from CLSG (where she also applied) and SPSG (didn't apply but we used their maths papers in particular).
She didn't go to a prep school and she didn't have any friends applying in 11+ as she was at a straight-through school outside the traditional British system. I looked online at what is considered 'creative writing' and was shocked to see how un-creative the creative writing part is expected to be! Essentially it's descriptive writing with formulas like the 'power of three' etc. that need to be in there to get the ticks.
For interview prep, we just practiced conversations as she wasn't particularly good at articulating her opinions then. We did go through each school and have her think of a couple things she liked about each in case one of them asked. Nothing prepped or rehearsed, just more getting her used to elaborating on things and showing who she was.
The LUS interview consisted of, if I remember correctly, being shown a close-up picture of something and being asked to try and work out what it was. The focus seemed to be on seeing how the children approached the task, what questions and ideas they had, and so on. Then a general chat. The interviewer picked her up at the table in the chaotic dining room, and brought her back. She'd fiddled so much she'd broken her mask and the interviewer was teasing her for that, making it clear to me that the interview had gone well. She left thinking that the dining room was beautiful and really, really wanting to know what the picture was of! It was a positive experience for her.
Good luck to all the kiddos going through it now. It is so stressful watching such little kids go through such a brutal sorting process but ultimately I think the kids are more resilient than the parents as we want to protect them so much from all this! So good luck to all us parents too!