Convert 320VDC to 220VAC or 48VDC voltage using 220VAC (UK) UPS?
Solar energy from solar panels, when not being able to be consumed at the rate at which it's being produced (almost always the case), has to be either of the following: 
- stored (usually in a battery) or 
- fed back to the grid (e.g. a grid-tied system), or 
- dumped into a dummy load (usually just beefy resistor packs) to convert the energy to heat 
the energy has to go somewhere.  

So it sounds like what you're interested in using the UPS as the battery bank, but your UPS system probably is designed internally to only charge its batteries from A/C power, where as your solar panels will give you D/C.

You could theoretically (but maybe not very practically) use an inverter to convert your D/C to A/C (if one such inverter existed with such voltage levels input/output specs, wouldn't really surprise me though), and then feed that A/C into the UPS (since the inverter would essentially just give you a normal wall outlet to use), but that would probably just be rather wasteful (e.g. not efficient due to the D/C->A/C in the inverter and then the A/C back to D/C within the UPS (and eventually you might want to go back to A/C for your appliances running off the UPS).  

What you might try instead (although this is hardly trivial) is to disassemble (carefully) and try to tap into the battery banks of the UPS directly and figure out what voltage it works at (likely 12, 24, or maybe 48 volts DC).  You could then theoretically step down your solar panel's output using some kind of custom (or off the shelf, it anyone knows of one) DC-DC converter, then you can feed that into a battery charger, preferably an MPPT type one.  Those kinds would adapt the incoming power to what would be most suitable to charge the UPS batteries to do maximum power point tracking (what MPPT stands for) and reach upper-90% efficiency.

Or if possible (and i don't know if it is) re-arrange the solar panels such that they don't give you 320 volts (are you sure you don't mean watts?) but give you a lower voltage at a higher current rating.  Otherwise you'll likely be hard-pressed to find a battery charger that accepts 320vdc to charge the batteries of your UPS.