Hello, sorry I was offline by the time you had replied. It does appear that the company wants you out and they have already approached you with the possibility of leaving under a settlement rather than them having to try and find reasons to dismiss you. There is nothing wrong with making a settlement offer, but you have to consider whether the reasons they may use to dismiss are going to be genuine. Unfortunately without knowing exactly what the allegations are and what evidence they have it can be somewhat difficult to pre-empt whether they will be able to justify any dismissal as being fair.
If you are adamant that you will not be able to return after all this, then the best option is indeed to try and leave via a settlement agreement. How you negotiate a higher pay out is unfortunately no straightforward matter and there is no magic way to go about it. In the end it will be a question of what you are willing to accept and what they are willing to pay. Neither party can be forced to accept an offer they are unhappy with so it is all about finding mutual ground.
What you can use to your advantage in negotiations is to make it clear that you do not agree with the reasons for any potential dismissal and that it clearly stems from the recent issues you have had, coupled with apparent age discrimination. So if you cannot agree on a figure, then assuming they go ahead and dismiss you, you would be seeking to pursue a claim in the employment tribunal for unfair dismissal and age discrimination and they would have to send a lot of money and time defending this and proving to the tribunal the dismissal was indeed fair and not discriminatory. Instead they should simply give you an improved offer and avoid any of this nuisance, ensuring a clean break between you.
This is your basic legal position. I have more detailed advice for you in terms of further negotiating options you have before you can make a claim in tribunal, which I wish to discuss so please take a second to leave a positive rating for the service so far (by selecting 3, 4 or 5 stars) and I can continue with that and answer any further questions you may have. Don’t worry, there is no extra cost and leaving a rating will not close the question and we can continue this discussion. Thank you