About a year ago I started a job, my contract for it says:
Pay and Expenses
The Employee will be paid £9/hr in arrears. Salary may be increased at the direction of The Employer subject to The Employee taking on additional responsibility which is agreed upon by both parties.
If the Employer makes an overpayment to the Employee to which she is not entitled, or which is more than that to which she is entitled, the Employer has the right to recover the overpayment by deductions from the Employee's salary or from other payments due to them. Any deductions will normally be made over the same period that the overpayment was made.
Notice of termination
The Employee is obliged to give the Employer 4 weeks notice to terminate their contract of employment.
A couple of months into the job my employer thought I was planning to quit and as they didn't want me to I was able to negotiate a pay increase to £11/hr, and my employer asked that if he gave me a new contract with this pay increase would I agree to work there for 2 years. At the time I said yes however no written contract containing our agreement was produced, so the only documents I have are my original contract, my pay however did go up.
Now however due to a change in circumstances I would like to quit and I'm wondering if my employer could reclaim all the additional pay they have given me over the months if I do.