Morning Darren
The obvious one is BMW ISTA/INPA not the cheapest but by far the most comprehensive and gives Dealer level access. Require a little patience to master but well worth it (my opinion)
Then there are systems by Autologic, iCarsoft, Bimmerlink and Foxwell, all work well but are not as comprehensive as ISTA/INPA (mine has WIS and TIS). There are also a few systems which are Subscription led such as Carly
Personally if I have tools I want to own them not rent them so I prefer to buy the complete package (on an old laptop that lives in my garage I have Diagnostics programs for Volvo, Merc, VW, and BMW. Plus an Autologic scanner and a BMW iCarsoft scanner (I am a born tinkerer and a boy needs toys)
One diagnostic session at a Dealer will probably cost close to £200 plus any remedial work they can recommend?? So owning your own which will allow adaptions, registration and reprogramming work to be carried out will save £££ in the long run.
Good Luck
Dave