I got this reply from the Devon Traditions coordinator at the wren trust, very useful -

Dear Thomas,

This appears to be the song Tammy-A-Lynn or Bryan-A-Lynn (Roud number 294). The version as you write it below is not in the collection, but there are a good few versions of the song.

Usually the first line goes "Tammy-a-Lynn was a Dutchman born", although from that point it differs (and as you can see, the version you have found has been localised to a greater degree). It was collected in Halcombe Burnell and Lewdown. These versions collected in Devon by Baring-Gould are from around 1890 and have 6 verses. I've taken a clipping of one version and attached it to this email for you to see.

There is also a cutting from a newspaper relating to the song, under the title "Arts and Crafts on Dartomoor in 1837", describing it as a song sung by children when wool gathering. This goes:

Old harry Trewin, No breeches to wear
He stole a ram's skin, to make a new pair
The Skinny side out, and the wooly side in
And thus doth go old Harry Trewin.

You can see the search for all songs with that Roud number here -

http://library.efdss.org/cgi-bin/query.cgi?index_roud=on&cross=off&type=Song&access=off&op_9=or&field_9=&op_12=or&field_12=&op_13=or&field_13=&op_14=or&field_14=&op_15=or&field_15=&op_47=or&field_47=&op_16=or&field_16=&op_0=or&field_0=&op_17=or&field_17=&op_10=or&field_10=&op_11=or&field_11=&op_18=or&field_18=&op_19=or&field_19=&op_20=or&field_20=&op_21=or&field_21=&op_22=or&field_22=&op_23=or&field_23=&op_24=or&field_24=&op_5=or&field_5=&op_25=or&field_25=&op_26=or&field_26=&fieldshow=single&op=or&query=294&field=20&output=Record&length=5&submit=Submit+query


I hope that's helpful, and if you need any further clarification, please don't hesitate to get in touch,

Kind regards