I've spent a long time as a legal academic but on the professional side - GDL, LPC, BPTC. I currently work in a department that has both LLB and professional courses in a -former polytechnic- post-1992 university.
There is a hierarchy of institutions and what they do. A Russell Group law department is unlikely to have much interest in professional areas. Most of the staff will never have practised. They will, though, have had an academic career, doing LLM and PhD. They will be very research focused - the classic complaint from students in such places is that the staff are more interested in their research than in them. That may start to change as the Teaching Excellence Framework comes in over the next few years. On the other hand, the students tend to be very able. The challenges of teaching do depend on the quality of the students; there is a great difference between working with someone who can spot the flaws in a Supreme Court judgment on a first reading and someone who has difficulty grasping the concept of offer+acceptance+consideration+intention. Some people prefer one sort and some the other. Getting into such an institution from a professional career is likely to be difficult, unless, perhaps, you have outstanding LLB qualifications such as an Oxbridge First.
Below them in the hierarchy are the universities that were polytechnics and had established law schools prior to the 1992 upgrade. Many, though not all, offer professional courses, and it is sometimes possible to teach cross-programme; I know people who have started on professional courses and then leveraged themselves over to LLB ones. The students are likely to be those who couldn't make the grade for more prestigious institutions or whose university choice is constrained because they are unable to move away from home. The focus is on teaching and research takes a back seat; many of the staff will only be nominally research-active. These institutions may be more amenable to someone from a professional background and may be prepared to put you through a PhD. (Compared with other disciplines, PhDs have been relatively rare in law but the universities are now trying to bring law into line on this.)
At the bottom are the universities that gained status after 1992 - these are a mixed bag. They tend to have the least able students and again concentrate on teaching them rather than research.
The wild card is the private sector universities; BPP and the University of Law. They have a limited presence in the LLB market and are aiming their courses as, as far as I can see, feeders for their professional courses.
Workload is pretty high on professional courses but maybe a bit more forgiving on LLB ones. In a classic university there are no fixed hours as such - you simply have to be there when needed - so at the moment, for example, I am nominally working at home on material for next year pending the arrival of the final marking for the year on Monday. However, some departments do part-time courses which require evening or weekend work. There is quite a lot of scope for ducking and diving and dodging and weaving. As in any career, it sometimes seems that the best way to avoid real work is to get some management responsibilities . . .
Compared to practice pay is capped. The career grade is generally Senior Lecturer, which maxes out at about £47k full-time. There are posts beyond that but they are relatively scarce. Pay has been held back for 8 years now - universities are currently far keener on paying builders than they are on academic staff.
As others have suggested, one of the best ways in is to wangle your way onto sessional work if your existing job will allow this. This allows you to mix metaphors and get a toe in the water and a foot in the door. One downside is that a lot of people move from one institution to another to climb the career ladder, which is fine if you are mobile but less so if you aren't.