Lampoc

Assuming you're in the UK, you'll be hard pressed to get a mechanical movement serviced by a professional watchmaker for less than £100, never mind a twin barrel Slava. You might find some guy on eBay with a £15 Amazon watchmaking kit willing to have a go for under £50 but you take your chances. I remember sending about 6 watches to a guy in Ukraine for service because he was super-cheap - within a year all of them had stopped working... I wouldn't start swapping movements around - there are far too many variables for it to be worthwhile. It sounds like your Slava has a problem with the balance - possibly a broken pivot/jewel. If you have a spare Slava movement, first thing I'd do is swap the balance over.

I'm pretty sure it's a version of this Slava (3993800) The catalogue says gold plated:

Wostoks were for the German market as they pronounce "W" as "V".

That's pretty cool and I kind of want it despite having a modern one!

Also check out: https://soviet.market/ (will mod a watch to your specs) https://komandirskie.com/ https://online.vostokinc.com/ (The Vostok factory website and also the cheapest place)

That's a modded Vostok. 020 case with aftermarket sword hands and what looks like an AM Watches bezel.

No idea if it's better! Probably not as it had a pretty poor reputation for reliability in the first place. I have plenty of spares though. If you order direct from Slava it's pretty easy to knock another 15% off (already tried) and yeah, £500 might be a bit risky but I really, really want one ;)

Raketa is the obvious one. I've one of the modern ones and it's a pretty decent watch. Slava also make some interesting reissues that are around the £300 to £500 mark but I've no experience of them - hopefully that'll change soon as I intend to splash out on one the new "Televizors" Konstantin Chaykin if you have seriously deep pockets. My Raketa:

Beijing watch factory are supposedly pretty decent: http://en.beijingwatch.com/index Fiyta make some interesting chronographs.

Looks like Camy registered "Vostok" as a trademark the day after Yuri Gagarin's spaceflight on 12th April 1961. The Soviets obviously (rightly) ignored it!

Most Komandirskies still are plated brass. Some of the newer ones such as the 650, 350 and 020 cases are steel - you can tell by the third number in the sequence (0=steel, 1 = chrome plated brass, 9=Titainum Nitride plated brass). The crystals on these watches are made of plastic for a reason - they're designed to deform under pressure to increase water resistance. As long as the watch back and crown are properly sealed, these watches are cpable of going down to much more than 200m. I have one that's been tested to 800m before it failed! Scratches are easily polished out using products such as polywatch.

Next purchase: bigger Vostok watch box ;)

All the straps on the Meranom site are real - most just have a small 'B' on the clasp. Yes fake Vostoks are a thing. If you're unsure of a watch on eBay post it up here and I'm sure someone will give you an honest opinion of it.

I haven't seen decent branded Vostok dive straps for a while. Someone used to make these but I've no idea if you can still get them: The bog standard Meranom ones for £7 are pretty good though: https://meranom.com/en/amphibian-classic/straps/silicon-strap-anti-dust-20mm-black.html

Some Amphibia crowns are plated, some aren't. Not sure why - these 2 models are on Meranom at exactly the same price but the sniper dial has a stainless crown while the KGB dial has a plated crown I'm not sure if the bezels are plated/plastic (I looked at one of mine and it seems plated and plastic?) but they are cheapest non-standard ones at Meranom which should tell you a little ;)