Ok,
After growing up in Bournemouth, living there for over 25 years, surfing there for 10 years, I've seen the place be really, really good and really really crap.
It's not that great as a "beginners" wave as the peaks are focused on Bournemouth and Boscombe piers, which have crowds of over 100 people at the worst of times. The other is Southborne, where the wave is a sucky shorebreak, not really suitable for anything apart from bodyboarding, although you do get the odd decent standup who can manage the takeoff and get barrelled.
I would recommend Highcliffe, the other side of Christchurch. It's not so busy here. The waves can be long and fairly slow, so perfect to learn on.
Kimmeridge ledges can be sketchy due to it being over rock. Often, the main hazard is getting in and out of the water, due to all the holes in the floor that you can get your leg trapped down. Once you are in the water though, it is extremely easy to get "out back" although can be a long paddle, perhaps 250metres some days. It was one of my favorite spots and when I first started, it was always quiet over there. You'd pull into the car park by the ledges and there might be 3 or 4 other cars there. Last time I went, just over a year ago, we pulled up and the car park was totally full, as was the car park by the toilets, with the main clifftop carpark looking busy too. This was at 7am on a weekday. I refused to go out as I won't get involved in the whole crowd thing, having to fight for waves etc. We went and checked out a secret spot to the east which involved a proper long walk but was worth it and had better waves and nobody else surfing!
I would keep an eye on magicseaweed.com's forecasts. You can get an iphone app for it so you get alerts if it's "5 dark stars". These forecasts take into account swell size, period, direction, wind direction, fetch and tides, so does all the work for you.