Paralegals work in solicitors' firms; paralegal law firms; the in-house legal departments of large companies; in central and local government; for charities and the not-for-profit sector. Even the military uses paralegals.
Who doesn't use paralegals? Barristers' don't - barristers' clerks are not paralegals. Legal executives are usually employees of solicitors so they rarely do. Notaries tend to work alone and law costs draftsmen arguably don't usually practise law at all (although they do provide a vital support service to lawyers).
In local government paralegals work in trading standards departments; parking prosecution; benefit fraud prevention; estates management etc.
Remember though, that outside the traditional legal profession the term 'paralegal' is rarely used. For example, in the Independent Police Complaints Commission paralegals are called caseworkers.
When looking for work, think flexibly. Entry level paralegal positions in solicitors firms are by far the hardest jobs to get. If you are unsuccessful, get a job somewhere else, learn your legal skills there and then transfer across later.