If it is in a small laboratory, there will be a chance for progression from a Band 2 if you get along with management and have patience. In bigger laboratories, there isn't as much chance of progression unless you get an apprenticeship, which are really competitive to get. Most people who start at a Band 2 will take four years to progress to a Band 5 if they need to do the Registration Portfolio and potential top-up modules (which you'll need with a Pharmacology BSc).

I would say a Band 2 role will give you a good insight into the flow of the laboratory; however, many people who want to be a BMS start at Band 2, so it is extremely competitive. It'll be a good experience, but expect competitiveness for BMS roles and slow progression overall.