Legally you can contribute to any pension you want. The particulars of your current company scheme may not allow salary sacrifice into anything but their scheme though, often thatís the case if the company contributes on your behalf or matches some or all of your contribution. You would need to check the particulars with your company or the scheme trustee.
In situations where the company contributes on your behalf itís sometimes possible to forgo that and get it added direct to your salary (normally a lesser percentage though).
If thatís the case you could then add that to pension 1 (if that scheme allows you to still contribute to it) or indeed you could apply it to a SIPP and gain the tax relief on it that way.
And also just because Pension 2 has a maturity date of 67 doesnít automatically mean you canít access it early. Again depends on the type and particulars and their may well be implications in terms of value but it should be possible.
DC and DB pensions also work differently so it may also depends on what type of pension you have.
Finally your Pension 1 scheme may say 55 as the date but effectively thatís just the state pension age less 10 years (the earliest date anyone can access any pension). Worth checking what your state pension age is as itís changed a lot recently and is currently tapering up to 67. There is a handy wee table here to tell you what it will be:
So in my humble opinion there is no straight answer here (there rarely is when it comes to pensions!) and you will need to engage with your company, the relevant schemes and maybe take some financial advice...