ER internship in London

I am currently studying in a Dutch University starting a 12 month Msc Finance program. After my studies I would like to work in ER in London. It is clear that I need to do an internship to have any change in FT hiring. One option is to go for summer internship. All BBs have ER summer internships and I am pretty sure that MMs and boutiques as well. No doubt the competition for the few ER positions is tough. On the other hand I could try for off-cycle internship in next fall after I graduate. Off-cycle Internships are usually longer (3-6 months) Does this mean that you can learn more an therefore increase the change of a FT offer? One immediate pro of off-cycle is that since the hiring starts later in the year I can use my master grades (which are surely going to be better than bachelor grades). One con I can think of is that I am not sure how many smaller ER houses offer off-cycle internships. Therefore I am afraid if don’t get an offer from BB and will be left without any back up plan. I would appreciate your thoughts on the topic.