The full answer to this depends on a lot of factors...1. Logistics – yes, it’s possible as you’ll only be expected at one place at a time.2. Contractually – depends on whether your employment contract exclusively prohibits you from providing competitive services while in their employ – quite common.3. Tax – situation will be more complicated that for a normal contractor as you will have both employment and “self-employment” benefits in the same tax year. Tax efficiency will not be as high for you as it would be for contractors with no employment income.4. Getting the job – will work if you have an offer already and they are willing to wait, but it is very unlikely that any agency will want to take you on as a contractor knowing that you are an employee on a break.5. Career – will look very strange on your permanent CV – unless you claim to have been travelling instead.