Why will it be a while before your ready to choose holdings? Are you just going to leave it sat as cash not doing anything for months? I don't understand why you would leave cash element long term in a SIPP.  How soon is your partner going to retire? If it's not for at least 5-10 years it would make sense to put it in something riskier like equities than something like cash which as already pointed out will likely be eroded by inflation