Rejecting Item After 6 Months (and two failed repairs)

[Guest]

So I purchased a product back in April which developed a fault within the first 6 months, within this time, I asked for a repair/replacement. The product was sent off but I received it back with the exact same problem (but was told the problem existed and had been fixed). I asked for it to be replaced/repaired again and the product was sent off, same scenario again however, product returned without being fixed, although was told the issue had been fixed.
I then exercised my final right to reject the product, which by this time was November, beyond the 6 months from returning it.
After being told 'we can't offer you a refund' for a month, they have now offered me a partial refund of about 60% of what I paid, providing I return the device to them.
I understand the Consumer Rights Act says the retailer cannot make any deductions from a final-right-to-reject claim if it was exercised within the first 6 months from delivery. Mine is outside this window, but only because they failed to fix the problem twice. I informed them the product was not working within 4 months of delivery.
Is there any way I could still receive a full refund? The deduction is for the amount I would have been able to use the device before refunding, but I haven't been able to use it since 4 months after delivery.
Any help would be greatly appreciated!
This all occured in England
Cheers

(also the problem was actually there from the start, it just took me a while to realise it wasn't me using the product incorrectly - it was a camera stabiliser so it was hard to tell!)

[ostell]

THe clock stops from the first notification of the fault to the satisfactory repair.

[des8]

As you point out not only should there be no deduction for usage as goods rejected in first 6 months, but trader also has to pay for cost of return.
Read Consumer Rights Act 2015 Consumer Rights Act 2015 (legislation.gov.uk) and depending on how much is at stake tell them you are considering court action.