OP, all you need is practice, confidence and a brilliant driving instructor (if you live in North London I'm happy to recommend you mine).
I first tried learning when I was 22, wasted money on 30 lessons with a crap instructor who kept telling me all about her problems with her husband and MIL, and then gave up because I couldn't afford any more lessons and suspected that I was never going to be any good at driving.
I started again two years ago at the age of 38 when on maternity leave, thinking how hard could it be to pass my test before going back to work - er, very!
It took me about 130 lessons over two years, the first half with another rubbish instructor, who also used me as a free psychotherapist - so I learnt more about her problems with her boyfriend than about driving - kept me going round in circles in second gear for 15 lessons, and then never took me above third gear or on anything more complex than a high street for the next 50. And kept cancelling my lessons so that some months I'd be lucky even to have one.
It wasn't till I found a new instructor, who's been teaching people to drive for 50 years, kept his conversation to a minimum, made me go on a dual carriageway on our first lesson, and told me I had technical ability but no confidence or judgement, and gave me three hours of practice every week, that I actually made progress, and actually really, really wanted to pass my test. Which I did first time round. 
If I can do it, anyone can do it, OP. I so enjoy driving now that I wish I'd persevered and passed my test 18 years ago. But I agree with other posters, if roundabouts scare you, then you shouldn't be taking your test again so soon - or at the very least you need to really concentrate on your Highway Code, because everything you need to know about approaching roundabouts is in there.