" A Building Survey (formerly known as a ’ full structural survey’) is an RICS ‘Survey Level Three’ service. A Building Survey report is based on a detailed , visual inspection of the building, its services and grounds and is more detailed than an RICS ‘Survey Level Two’ report."
It would seem that you could have had a full structural survey ? , if the surveyor didn’t pick up any subsidence it either has only recently happened, or they missed it - don’t know without any further info , however if they missed it they were presumably RICS ( Royal Institute of Chartered Surveyors ) members which should have included professional indemnity insurance during the period of the survey ??? which is perhaps an avenue to pursue in a claim on the original survey.
If they didn’t miss it - because it wasn’t there when you purchased - you could potentially claim on your house insurance for the subsidence which has perhaps recently happened because you have this professional RICS structural survey prior to buying and insuring your house that doesn’t bring up this problem.
Bulging walls could also be attributable to the new or existing subsidence, again either professional indemnity insurance from RICS registered surveyor or buildings insurance ( required for a mortgage ? ) could rectify this, in the case of the latter with an excess paid by yourself (£1000 ? )
Doorways without “proper” support - do you mean timber lintels ?? which were common in earlier buildings or no support at all ?