**edit** rhm beat me to the punch..
Here's some info from ClassicRendevouz about Sun bikes
"Sun first began the production of cycle parts in 1885 and by 1906 were producing a range of machines. Their main period of fame was from the middle 20s through to the 50s. The Wasp was a popular almost budget priced lightweight aimed at the Clubman. Tandems represented quite a large part of their output. In 1940 they launched a new version of the Manx TT model which did not enter manufacture until 1945/6. It featured a seat tube joining the down tube about 2/3s the way down with a couple of extra struts from the bottom bracket to the seat tube. All this was done to make a short wheelbase which was seen as desirable then."
"Frames from the late 30s right into the 50s were also marketed under the Parkes name. In 1959 they became part of the British Cycle Corporation which was absorbed by Raleigh in 1960. From 1963 Sun machines bore the badge with Worksop rather than their original Birmingham. The name finally died under Raleigh in 1986. There a few good quality Team Replica bikes from the Sun/Truewel Racing Team made in the late 60s."
"Peter Cowan, the Veteran-Cycle Clubıs Marque Enthusiast has written an excellent potted history of Sun on which this account of mine is based. It is available from him at The Old Forge, Lyonshall, Herefordshire HR5 4DL Great Britain."
So your bike is technically a "Sun" made bike, although they were owned by Raleigh at the time.
Most likely a gas pipe frame, fairly heavy, but would clean up nice to ride around town.