Advice please repair or replace

[lew247]

I bought a Hitachi split unit air conditioner off that auction site a few months ago and recently had it fitted.
The installer said the service valve was leaking, he tightened up the cap but said the refrigerant will leak out over time, be it 1 month or 1 yr.

They did say it could be "silver brazed" but it would be really tricky and expensive to do it.

I've priced the service valve assembly and it's around £75 including postage, the person who fitted the aircon said it's going to cost around £250-300 to fit it and then recharge the system.

Is it worth my time and money getting it fixed, could it be done cheaper, or should I cut my losses and buy a new split unit?

Alternatively

Is it possible to use any other outside unit with my indoor unit? (my preferred option as it could be a lot cheaper)

I don't have a fortune as I'm disabled and not able to work unfortunately so the cheapest option is best for me.

The outdoor unit is Hitachi RAS25YH6
and the indoor unit is the RAC-25YH6