This is the Gov.uk summary of what changed on 29 March:
The ‘stay at home’ rule will end on 29 March but many restrictions will remain in place. People should continue to work from home where they can and minimise the number of journeys they make where possible, avoiding travel at the busiest times and routes. Travel abroad will continue to be prohibited, other than for a small number of permitted reasons. Holidays abroad will not be allowed, given it will remain important to manage the risk of imported variants and protect the vaccination programme. The government has launched a new taskforce to review global travel which will report on 12 April.
The British Cycling guidance (which is negotiated with the Dept for Digital, Culture, Media and Sport) is here:
https://www.britishcycling.org.uk/about/article/20200512-about-bc-news-British-Cycling-Updated-Coronavirus-Guidance-0I think Cycling UK's guidance about 'stay local' is slightly misleading. While you aren't allowed to stay away overnight, and you shouldn't travel a long distance in order to carry out a ride, there's no limit on how far from home you can go while exercising, so long as you don't cross into another jurisdiction with different rules.