Final Salary Pension, SIPP, and ISA

You are eligible for a SIPP. But it won't receive an employer contribution so it won't be especially attractive unless it lets you avoid higher rate tax.

One exception would be if you wanted to retire before 63; then you could draw income from your SIPP while waiting for the FS pension to fall due. If that were your only income at the time it would be tax-efficient because it would use up your Personal Allowance vs income tax.

The possibilities might include buying additional years in your FS scheme, or making AVCs. Neither of these would apply if your particular FS scheme doesn't offer them.

Yet another possibility would be a LISA from 17/18 onwards. That would let you draw income tax-free from age 60 but would be less attractive than a SIPP that lets you avoid 40% tax. Except that the LISA is more flexible than a SIPP: the LISA will, if it functions as advertised, let you withdraw money before age 60 at the price of forgoing the subsidy that the sum withdrawn would otherwise have included.

Is a SIPP something I should look into?

Why SIPP?
Why not stakeholder? Why not personal pension?

You are looking at potential solutions but what problems are you trying to solve?

Pensions are more tax efficient than ISAs due to the fact that you effectively get a rebate on any income tax you've paid on the money that will be used for contributions.

I.e, if you're a basic rate taxpayer and contribute £10k, the government will bung in an extra £2,500. If you're a higher or additional rate taxpayer, in addition to the basic rate top up you also get relief at your marginal tax rate (though this won't actually go into the pension, it just increases your nil-rate band for the next tax year).

It's generally a better option than an ISA if you're specifically concerned about retirement savings. The obvious downside is that you have to tie your money up until you're at least 55.

As Dunstohn says, make sure you choose the right product for your goals. If you're happy using the DIY approach, a SIPP with a provider like AJ Bell is a good option. If you want to just 'set it and forget it', a stakeholder personal pension might be a better idea, and they're usually cheap in terms of fees.