Hello again. First of all it is important to stress that a settlement agreement can basically include anything and does not have to reflect your contractual rights and benefits. Sometimes it can be more than what you are entitled to, other times it can be less. It depends on the reasons for termination and how much the employer is willing to negotiate a clean break. For example, the more they have been in the wrong leading up to the termination, the more incentive there is on them to offer you a more lucrative package so you accept it and leave without being able to make a claim in the future. On the other hand, if the reasons for termination are not so much their fault there would not be such an incentive to offer you more than the contract and it can even be less. Basically the settlement agreement is an agreement by itself which can overrule the contractual rights of both parties. However you do not have to accept anything you are not happy with.
So if you have not done anything wrong to prompt this termination, I would always suggest that you stick to at least what the contract would have entitled you to in normal circumstances, plus then potentially negotiate more based on how strong your position is in terms of challenging the reasons for dismissal (i.e. If there were no misconduct or performance issues and they simply want you out without there being a fair reason for dismissal, you may have more leverage to ask for this).
Under Clause 16 of the contract the employer does have the right to end your employment earlier than at the end of the notice period, but they would be required to pay you the basic salary and bonus and benefits to which you would have been entitled to had you been allowed to work that full period. At present they are asking you to work until March 2018 which is 2 months and then giving you pay to cover a further 6 months. You can request that they cover the full 12 months as per contract, although bear in mind that if they do then they are not obliged to stick with the current offer of an additional 6 months pay. Therefore they can say they will pay you 12 months pay and benefits as per contract but remove the 6 months offer which currently stands.
Also remember that provisionally accepting any offer does not bind you to it - you are still legally required to take formal legal advice from a solicitor before it is all signed off. Often, once the solicitor starts advising you they may find certain factors in the relationship and the circumstances of the case leading up to termination which may give rise to re-negotiate the existing terms of the agreement. So the terms could still be improved once you have spoken formally to a lawyer even if you had provisionally said you agree to them. The agreement is not legally binding until you have signed it off after you have been advised by a solicitor and the employer then also signs it.