The register is not definitive re such detail and the term 'tenants in common' is not referred to on the register.
Joint owners may indicate that they wish to hold the property as tenants in common when they are registered or may decide to sever their joint tenancy at some stage. When this happens, and where the land is registered, we can register a Form A restriction on the registered title, namely
'No disposition by a sole proprietor of the registered estate (except a trust corporation) under which capital money arises is to be registered unless authorised by an order of the court'
The Form A restriction does not itself change the ownership from beneficial joint tenancy to tenancy in common. The restriction only reflects the request or change made.
And conversely if a form A restriction is not present it is not definitive that you are joint tenants as you may have severed your joint tenancy in some way but never applied to register a form A restriction.
So it's important to look at both the registered information and also wider information such as your wills and more to ascertain whether you are tenants in common or joint tenants
For further information see Joint property ownership available on the
GOV.UK website