Can I justify buying this?
Well, you've told us a great deal about why you want a non-necessary item, but nothing about your personal finances.
Do you have debt? A surplus of cash each month? Savings? What are your financial goals?
The fact that you call a 42" "super small" and that it "just gets by for TV" says something about your wants
I'm debt free other than mortgages and UK student loan. The latter is both highly regulated and thus more a temp 9% tax and it's also about 8 months from being gone. My mortgages are:
Residential - £135k @2.32% fixed 3 years 35 years
BTL interest only - £86.25k @2.77% fixed 5 years
Currently saving around £700 a month (after all expenses including BTL mortgage), plus £2k bonuses each year. I've £19k in cash (currently renovating the BTL then back into vanguard ISA) and ~£45k in property capital. Both properties are in fast growing areas with strong yields. Estimated annual profit after payments, repairs, voids etc of £4,692.60.
Aim is to retire in ~9 years (36/37). I still need to rerun numbers after renovated flat is done and leased. That income will go into pension at first for tax advantages but will provide living income afterwards. I need £12k a year to live on and pay current mortgage. Presuming the rental flat stays the same (it won't but for the sake of argument), I need about £180k by the 4% rule. However I'll have my private pension by 60 and based on current calculations that should have ~£400k (ie more than enough), so the lump sum only needs to last 26 years. I still need to find a calculator for the math. I also plan to work as an actor after 'retiring' so will have some *small* amount of income. Plus tech consultancy work is an option (I program and do organisational change work atm).
tl:dr My financial goals and my plan to reach them are reasonably solid. This purchase wouldn't help but it would be relatively minor blip. I would also add that I'd expect any new TV to last minimum of 6 years warranty, ideally 10 years.
Also when I say 'super small' I mean for the space. Unfortunately there's no nice way to reconfigure the room to put the sofa and TV closer. I previously used a cheap secondhand 27" monitor up close for 5 years, it was great. But I can't see a way to make that work in my current place :( I've been there 4 months and have tried.