Canadian Nationals will require electronic visas (ETA) to visit the UK as a tourist beginning January 8, 2025. Applications can be made and entry requirements reviewed on the UK Government website https://www.gov.uk/entering-staying-uk. There is a fee, and all travellers in your party will require an e-visa in advance of travel.
If you are simply in transit through the UK you may not require an e-visa. The link below will help you check your individual circumstances and if in-transit be ready to show that you have onward passage beyond the UK.
Here is the link to check if you need a VISA where you can also input your nationality https://www.gov.uk/check-uk-visa.
Individual traveller's have responsibility, to know, understand, and complete all requirements for entry into a foreign country. Your travel agent can assist, but given the wide range of individual circumstance and the confidential nature of information that is to be provided, and the need for you to personally certify or declare your answers, travel agents cannot process theses applications on your behalf.
Changes are also coming to entry requirements for multiple countries in the European Union (EU) this year. Planning ahead will be important to smooth travels.