Training cost repayment

[Lilly1296]

Hoping someone can help me, I have signed a training agreement with my employer and have been attending the course for nearly two years however I have been offered a great job opportunity elsewhere and the only thing holding me back from resigning is the agreement below:,


If you decide to terminate your contract of employment during or within 12-months of completing the training, or withdraw form the course whilst still employed by *employer* the company will seek to recover from you a proportion of your fees paid.This calculation is based on a sliding scale as shown below.
*

Service	% Fee
Prior to commencement or part-way through the course	100
Withdraw from the course whilst still employed with *company*	100
Upon completion of the course	75
Within 6 months of completing the course	50
Within 12 months of completing the course	25

Declaration
I agree to the terms and conditions of this contract and authorise my employer,to recover from my salary any outstanding sums due in respect of the contract.

My question is how enforceable is the agreement I don't mind a deduction of final salary but the full course cost is £6k how will they pursue the remaining amount?
*

[ULA]

Unfortunately this is very clear and that there will be a requirement to repay the training costs at the relevant scale for your situation. If the amount owing is more than your final salary, then your company needs to speak to you about a repayment plan for the outstanding amount.