The magistrates will probably see the ABH offence as 'Category 3' (which is the lowest category). The 'starting point' sentence for Category 3 is 'medium level' community order, with the magistrates then having to work up or down from there. The lowest penalty they can impose is a Band A fine which, in turn, has a 'starting point' of 50% of 'relevant weekly income' and a range of between 25% and 75% of such income. ('Relevant weekly income' is take home pay if you're getting at least that much or a fixed figure of £120 in all other circumstances). The highest penalty they can impose is a 'high level' community order. (i.e. as long as the magistrates agree with me that it's a Category 3 offence, you CAN'T be sent to prison).
The Common Assault charge is unlikely to be sentenced separately but it might just push up the sentencing for the ABH charge by a very small amount.
So, as I see it, the magistrates will start in the middle of the Category 3 range, with a 'medium level' community order. They'll then be minded to move the sentencing down a bit due to you pleading guilty at the earliest opportunity. However the Common Assault offence might possibly prevent them going all the way down to the very lowest point available.
So my best bet is a 'low level' community order and/or a Band A fine (or perhaps a Band B one, which is between 75% and 125% of 'relevant weekly income').
See pages 177 to 180 here to read what the magistrates will actually have in front of them in regard to the ABH offence:
https://www.sentencingcouncil.org.uk/wp-content/uploads/MCSG-April-2017-FINAL-2.pdf
(As I've indicated, the Common Assault offence can probably be largely ignored anyway; it's the ABH offence which will determine the sentence. However, if you want to read the stuff about sentencing for Common Assault, it can be found on pages 189 to 192).
See here for what community orders can involve:
https://www.sentencingcouncil.org.uk/droppable/item/community-orders-table/