Hi Virginia,
Realistically it is highly unlikely that the birds that you saw were Nutcrackers. This is typically a very rare vagrant to the UK with only eight confirmed records, all of single birds, during the last 37 years (which includes three in 1985 and two in 1991). The last accepted record was in September 1998.
You don't say how many birds were in the group you saw, but even during 1968/69 (when there was a large 'irruption' and numerous individuals reached the UK) the majority of records were of individuals, with only handful of records of two or more (maximum six). There have been no unusual movements on the continent this winter.
There have been occasional unconfirmed reports in recent years, but none of these has been confirmed despite extensive searching of the areas by experienced birders, and at least one report turned out to be a misidentification (Mistle Thrush).
The birds that most closely fit the description you have given, in my opinion, would be Starling (which do sometimes give odd calls, and do give calls that fit your description). You may well say that you are certain that this was not what you saw, and if this is the case I don't have any other suggestions. Without photos it is usually very difficult to suggest/confirm identifications.
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