LONDON/STRASBOURG (Reuters) - Britain wants a stable relationship with the European Union for "decades to come" in financial services, Britain's finance minister Sajid Javid said on Tuesday, but received an instant rebuttal from Brussels.Britain left the EU last month and its large financial services sector will lose privileged access to EU customers from January 2021. Financial firms would be able to service those clients only in sub-sectors where rules are deemed "equivalent".Javid called on..