National deficits must remain below 3%,- the set of economic criteria to join the single currency are too harsh for us,- they mean we cannot join at present, according to the treaty of Maastricht,- our economy does not meet the objectives set out by the treaties and hence we couldn't join the Euro yet, or anytime since it's introduction in 1999.
Our policy makers and politicians want to remain in control of setting interest rates and target rates for inflation,- the European Central Bank sets these for Eurozone countries. This would mean we are unable to pursue some national economic objectives, for the sake of the benefits, or perceived benefits, the Euro brings.
We are very traditionally Euroskeptic as a public,- the public are opposed to it.
Current economic circumstances,- the Eurozone is no more resilliant than we have been, besides Germany (arguably not because of the Euro, but because of the nature of her export markets)
Inward UK investment has not fallen since we declined to adopt the Euro
The pound and Euro are not too different,- small fluctuations.
Trade with the Eurozone has not declined since they adopted the Euro and we did not,- so trade benefits would be small,- perhaps only real benefits for companies, rather than our economy as a whole, Euro/Pound price differences are small and tend to stay within a guessable range anyhow.
The Euro is yet to stand the test of time,- at the time of formulation British civil servants advised the government that it would be set to fail,- no EMU has stood the test of time yet.
The Irish crisis,- low interest rates from the ECB meant they had a boom in 2007, which lead to an expansion in credit and the property bubble,- with over exposed banks and the nature of the Irish economy, many warn that this could too happen to us.
We still like to see ourselves as British,- national identity etc.
The cost of introduction,- printing new currency.