Let me take a look at this and I'll get back to you with an answer in a bit.
The payment needs to be disclosed as it is taxable income.
Take a look at the share schemes section on page Ai2 here and the notes on the additional information pages here.
In the past, your payment would have gone into box 1 but as you will read in the notes, you should only complete box 1 if the payment has not been fully taxed. Yours has. Box 2 has been withdrawn from use. I queried this with HMRC a while back and it was suggested I use box 3 for the pre-tax payment and put the tax deducted figure in box 6. I submitted the client's tax return with a note in the white space explaining the source and so far, it's not been queried. I was told by HMRC that box 2 was withdrawn because employers were not dealing with the share payments correctly.
I hope this helps but let me know if you have any further questions.
I'm afraid that the income from the shares will be part of your overall income for the purposes of determining your eligibility for the personal allowance or not. The tax calculation will show that. Take a look at the notes on "adjusted net income " here. The additional information pages mop up income and outgoings that cannot go elsewhere in the tax return or other supporting pages.
You cannot not report it. The SA101 pages are where you report the share gain.