More than one personal pension - possible ?

Yes

A bit depends on the rules for triviality when you come to take it. At the moment all funds together (or a notional fund if you're already drawing a pension) must not be more then a certain amount, £15K IIRC. You say the contributions to your new SIPP will be low (£25K). I don't know whether this is an annual contribution or monthly, or whether you are suggesting it's the final fund (rather than a contribution). Either way, it's too much for triviality at the moment.

Rob Graham

Thanks for that. Just expanding the final point. If I keep the new, second pension down to a trivial amount (say)

Yes, the triviality rules require all funds to be added together and do not apply to each one separately (it's not difficult to see why!). In any case, the cash you get is subject to tax, unlike the 25% cash from a normally-taken pension plan.

Rob