I often look at legal jobs despite having not graduated yet just to see career opportunities for when I do graduate. Most top firms require minimum UCAS points, these UCAS points are usually what you had to obtain to get in to university unless you entered a different way (access course etc)
I did a foundation year as I just had AS levels but in year one I sat my A levels as a private candidate in the same subjects as I got my AS levels in.
You still have a lot of career prospects in the UK and abroad. Small firms probably will not mind too much on A level results or if you have them as long as you have a 2:1 or above. If you are concerned then it would be a good idea to possibly volunteer in law firms or try to get a part time job, that way you build up experience which works massively in your favor. Also if you are really concerned it may be a good idea to contact various law firms that interest you for career opportunities and asking them of their requirements. Some may accept a degree with no A levels and others you may find are very strict, then you will know where you stand.