UK Standard Visit Visa rules are a little more relaxed than predecessor.
(a) Now study for up to 6 months is permitted.
(b) voluntary work of up to 30 days is permitted.
(c) students aged 16+ can receive research tuition.
(d) Greater provision for academic visitors to conduct research on sabbatical.
(e) international drivers can collect as well as deliver goods/passengers.
(f) Swiss nationals do not require entry clearance as visitors.
As a reminder, work is not permitted unless expressly allowed by Appendix Permitted Activities