If your business is called Blue Travel but bluetravel.co.uk has already been taken, have a look to see if the domain is being used or whether it is a parked domain i.e. is there an active website associated with this domain.
If the domain is not active then you can find an alternative. However, if bluetravel.co.uk is an active domain then it is not wise to compete with it by buying the same domain with a different gTLD i.e. bluetravel.uk
Try to identify a domain address that is not going to competing with another domain if possible.