Its a complex area, and you need to be careful.
My belief is that holiday pay is taxable and you have to pay employee's NI on it. Regarding the pay in lieu of notice, it depends whether your contract of employment specifically makes reference to that you may be paid in lieu of notice (in the event of end of contract) then HMRC will say that both tax and NI is payable.
Note that this is different from redundancy payments, which are not taxable up to £30k.
You really need to ask your employer (who may be willing to informally advise, but won't indemnify against a HMRC decision, or seek independent tax advice.
It can usually be structured (the payment) to avoid the tax liability but it depends on the employer playing ball. There is incentive for them to do so - they won't have to pay the employer's NI or make payments into your company pension.
Lastly, if circumstances dictate that the payments would be taxable, you can avoid the tax by having the employer pay them into your pension scheme, if it suits you to do this.