You can send then a legal notice and demand your dues if not given you can approach labor court or dy labour commissioner

Do you have any emails or other documentary evidence that you would be paid extra amount

kindly clarify 

1. Send a legal notice to your employer to pay your dues.

2. If it's not successful, file a case against the employer in the competent court.

Was this agreement made with you was in writing?

If you hav any documentary evidences to prove this claim, you may first make a representation to the management in writing and claim the amount due to you.

If there is no proper response then you can opt for legal route to claim the amount due to you.

Before that you can gather evidence to fight it out strongly.

1. You should send them a legal Demand notice through your advocate.

2. If they refuse to pay even after legal notice then you can initiate recovery suit Under summary trail but mKe sure you have some written proof of promise made to you for paying 5000 pounds.  

1. Was the promise made in writing through a contract?  If the answer is yes then serve a lawyer's notice to the company to release the amount.

2. If amount is not released even after lawyer's notice then a suit for recovery of money can be filed in the competent civil court.

Do you have this offer in writing or just verbal assurance. Verbal assurance than legal solution is bleak. Otherwise also,legal notice can be for demand of 5000£, failure to which are will be constrain to take recourse of law for recovery.

See you can serve them a legal notice.for.recovery of amount , you can serve demand notice to company under IBC since amount is above 1 lakh also in case they fail on.notice you can file a insolvency petition before the nclt.

Serve a legal notice to your employer for release of your salary and all the arrears. It is advisable to consult a well experienced lawyer for the same.. 

You are entitled to gratuity as you worked for the company from nov 2013 to August 2019 

2) an employee completes 4 years and 6 months of continuous service in the same establishment, he is eligible to get gratuity as per the Payment of Gratuity Act 1972. ...

1. Since you have completed more than 5 years of service in the same Company (November 2013 to August 2019), you are legally eligible for Gratuity.

2.  The period of service in U.K., (as per your narration) is an internal transfer and since your date of leaving the Company is August 2019, which amounts to 5 years and 9 months' of service. 

3. Legally speaking, an employee will be entitled to gratuity, if he leaves the Company after serving 4 years and 6 months, which will be counted as 5 years of service.

Yes.

Transfer is as per company policy and not fresh appointment.

if an employee worked for 4 years and 8 months, the duration is considered as 5 years of continues service and he is eligible for gratuity. 

Since you were on the company rolls for more than 5 years and were in continuous service for a period of 5 years or more you are eligible for gratuity.

employee needs to have at least five full years of service with the current employer, except in the event that an employee passes away or is rendered disabled due to accident or illness, in which case gratuity must be paid

A person is eligible to receive gratuity only if he has completed minimum five years of service with an organisation

For example, if an employee worked for 4 years and 8 months, the duration is considered as 5 years of continues service and he is eligible for gratuity

Yes you are eligible for the gratuity. 

See you were part of same company you are for your work eligible for gratuity.

Yes you are eligible for gratuity