Amazon Uk have stopped selling Vitd3 over 1,000ius - apart from the spray type which is 3,000ius. The last lot of Vitd3 l bought was from Nutra-Vita website. l buy the 10,000ius Softgels 365 - l think they were £7.99 - l bought 4 and it was p&p free. They arrived the next day.
Amazon now list several different suppliers of the Healthy Origins brand - either 2000iul or 2400iu - but there are several others around. Just do a Google search for Healthy Origins D3 2400iu. I found four that are cheaper than Amazon.
No doubt there are other brands as well, but I have always used Healthy Origins.
My MS nurse said one cap in the summer and two in the winter, but you do want to get your level checked regularly.