Question to the HM Treasury:

To ask Mr Chancellor of the Exchequer, how many sales of property worth £1,000,000 or more there were in (a) the UK, (b) Scotland, (c) England, (d) Wales and (e) Northern Ireland in each of the last five years for which records are available.

Property transaction statistics by price band and geography are published by HM Revenue & Customs on an annual basis and contains data for several years.

https://www.gov.uk/government/statistics/annual-uk-property-transactions-statistics-2013

The current publication combines information on the price of property transactions for England and Wales together. The specific information for each country is not readily available.

The Land Registrars for those respective countries also release their own data.