Martin has asked me to post this on his behalf; he has limited internet access over the next few days but will follow up on any comments etc when he is able to!
Sounds like a Two-barred Crossbill….
A crossbill sp. I recorded this morning (Rod Moor) seems too similar to Two-barred Crossbill to ignore.
You can listen to a recording of the call <HERE>
Analysed by Magnus Robb. The calls and sonogram are unlike any other European Crossbill. It would be good to get recordings of Two-barred from this year in Scandinavia. ……….meanwhile…….a possible Two-barred Crossbill (or bird calling like a Two-barred Crossbill ) in Rod Moor area (NW Sheffield) this am etc. Always learning!