Just finished the ULaw LLM course. I passed the SQE1 fine, but had to delay the SQE2 (from October to January) because there was no way I was going to be ready for it. In my experience, having to take the SQE Plus courses really got in the way of prepping, and I forgot a lot of the FLK I had built up for the SQE1 during those three months. Having an extra degree will be nice, but not sure I would opt for the LLM course if I could choose again.
If you do end up doing the LLM, I would just make sure that you start prepping for the SQE2 a lot sooner than when the SQE2 course actually starts for the programme