It certainly should be possible - the new s.4B TCGA expressly provides for losses to be set against the gains attracting higher rates (ss.(1) expressly refers to ss.(2) which describes the situation).
The losses on shares appear to be deductible from residential property gains at Box G14 in the calculation worksheet (SA110 Notes ), which (rather helpfully for HMRC) appears to set them against resi and NRCGT gains before other gains. I don't make a habit of completing SA108 but it looks like you just set out the losses there and the deductions take place in the calculations.
I don't know whether this has passed through into the HMRC or commercial software.
Osborne Clarke LLP