I asked this question and the salesman told me it would be locked
there is a way to unlock it later on but I don't know what this is
However, if you look at buying outright from Apple + Vodafone monthly cost (first 6 months free with connection only) you will see its actually cheaper over 24 months then buying on a 24 month contract
Since you have an EE account I am not even sure why you are asking about Vodafone as you couldn't use a watch contract from one provider with an iphone contract from another
Since you have an EE account I am not even sure why you are asking about Vodafone as you couldn't use a watch contract from one provider with an iphone contract from another