Stuart Scott's Battle Axe Blenheims : ISBN 0750911263 mentions P/O Shirlaw as having attacked Dusseldorf on 28th. November 1940. He was flying "T1932:T and along with another Squadron aircraft, started fires in the docks area".
On 31st. December 1940, he piloted "Blenhiem T1848:V and tried to reach an oil refinery in Bremen but had to give up because on lack of cloud cover".
The book also indicates the loss of P/O Shirlaw by the following "There was no sign of Q-Queen T1892. P/O Shirlaw and his crew P/O Dugdale (Observer) and F/O Mair (W/Op/AG) failed to return". The aircraft is recorded as "having hit a balloon cable at Pilton Hackett, SW of Birmingham". The crew is mentioned in the Squadron Roll of Honour and had service numbers 81054, 84034 and 78277.
For all the Blenheim types on the forum, I would thoroughly recommend this book.