TM111 is currently on its first presentation, and TM112 will be on its first presentation in April. I'm afraid you're in uncharted territory.
I'd had a whole paragraph about the weird April time start, but just read on the TM111 website that October and April, not October and February, are the planned start times for both of these modules going forward, so had to edit the whole post. (This seems directly contrary to the OU's "Students First" initiative, as it will result in students studying year round without a proper break their first two years.)
With this information, it seems unlikely that you'll be allowed to take both simultaneously, but you may want to call and ask about the possibility of special dispensation from the TM112 module team. It doesn't seem likely to me, but it's worth a call.