Vanguard are still trying to determine whether I lost out due to time out of market (I didn't really).
At the risk of digressing...
Here's my experience trying to transfer funds out of a current Scottish Widows DC pension scheme into a SIPP with ii. SW confirmed partial transfers were permissable. And their documentation inferred total flexibility.
Funds held in SW
Equities - International
Equities - UK
Equities - EM
Cash - MMF
SF100 to SW: I'd like to sell & partial transfer some of my cash to my SIPP.
A: no you can't do that, sales are done on last in first out basis (meaning I'd need to sell equities as well).
SF100 to SW: This is ridiculous. Let me speak to the manager.
A: ditto.
SF100 to SW: This is ridiculous. I'm complaining, here it is in writing.
A: (after several weeks/months) complaint not upheld.
SF100 to ombudsman: ditto, here's all the email correspondence and fund paperwork.
A: (after several weeks/months) ditto, SW don't need to play ball, not upheld.
After some procrastinating, thought I'd test it out in practice for a small amount to see.
SF100 to ii: I'd like to transfer £1k from SW to ii, funds to be taken from Cash MMF.
ii to SW: ditto.
SW to ii: there are several funds within this DC account, which fund is to be sold down by £1k?
ii to SF100: ditto.
SF100 to ii: sell down the fund stated on the transfer request.
ii to SW: ditto.
SW to ii: we have sold down Cash MMF by £1k. Here's the cash.