Looking through Air Britain's "The British Aircraft Specifications File" there is no mention in either B.9/32 which led to the H.P.52 Hampden prototype nor Spec 30/36 for the production aircraft of including a torpedo carrying capability. The latter lists the various bomb sizes to be included with no mention of torpedoes.
Hampdens were converted to the torpedo carrying role in early 1942 due to a shortage of torpedo carrying Beauforts to allow expansion of Coastal Command's TB force in the U.K. Two squadrons (415 & 489) were issued a few Beauforts in late 1941 only to have them withdrawn for issue to other existing Beaufort squadrons about to be shipped overseas. Instead they were issued with Blenheim IV until enough Hampden TB.I became available to fully re-equip them for the TB role in early 1942. In April 1942 Coastal Command was strengthened by the transfer of a number of squadrons from Bomber Command. Those included 144 & 455 with Hampdens which then also converted to the TB role. 3 of these squadrons then converted to Beaufighters in 1943 while 415 traded its Hampdens for Wellington XIII and Albacores in Sept-Nov 1943.
It was also early 1942 before the Wellington began to be used as a TB in the Med, again due to a shortage of Beauforts.
On the other hand, Spec P.13/36, which led to the Manchester and the Halifax, did initially include a requirement to carry two 18" torpedoes internally. As discussed in other threads this requirement was dropped fairly early, IIRC, in the development process. A number of other initial requirements were also dropped along the way before these types entered service.
Spec B.12/36 that led to the Stirling laid out the weapons it was to carry. These were a variety of types of 250lb, & 500lb bombs and the 2,000lb AP bomb. Again, no mention of torpedoes. None of these was wider than about 13-14" i.e. less than the diameter of a standard 18" air dropped torpedo. The bomb "cells" themselves were 19" wide, which would not have left enough working room around a torpedo to allow it to be loaded.
The Beaufort carried its torpedo "semi recessed". The main bomb bay was designed to house 4x250lb or 2x500lb or 1x2,000lb or a single torpedo. To accommodate the torpedo, the main bomb bay had fore & aft extensions, offset slightly to port to accommodate its full length.