I assume you mean higher inside (e.g. living area) temperature? If so yes, it sounds like your system can do it. Remember: when running minimum input electricity (say 900w), it can’t use less, so artificially limiting output won’t always reduce electricity usage. It’s counterintuitive at first.
Is your Tado set to crazy temp say 30C? (To ensure “on” is sent and kept “on”)
Is it doing anything like TPI (which is bad for heat pumps)?
See this post for one of many negative comments on TPI and heat pumps:
Interesting why Octopus 
didn’t install the Madoka as I thought that was standard.
If you’re running at dT of 5C (between flow and return) already, then you’re at the likely optimal configuration. You don’t really want to go lower than this as it’s likely this is most efficient.
What is your maximum flow rate you’re seeing when in heating mode?