Nothing much is likely to happen at the magistrates court, other than that they'll then pass the case up to the Crown court. They'll do that because the quantities involved, and the number of offences, will suggest to them that their sentencing powers might be insufficient. The maximum sentence magistrates can pass is 6 months for a single offence or 12 months for multiple offences. However that doesn't automatically mean that you're going to prison; Crown courts frequently impose non-custodial sentences (or suspended custodial ones) even though the magistrates who referred the case up clearly expected something more.
The first hearing at the Crown court will simply be a formality as well. ('Plea and case management').
See pages 3 to 8 here to read what the judge must consider when passing sentence:
https://www.sentencingcouncil.org.uk/wp-content/uploads/Drug_Offences_Definitive_Guideline_final_web1.pdf
Diazepam (when purchased through 'legitimate' sources) is sold in 2mg, 5mg and 10mg tablets. A 2mg tablet might weigh 0.15g, so 182,000 of them could weigh around 27.3kg. So, even if you'd got the smallest tablets, that's a hell of a lot of drugs, possibly putting the offence around 'Category 2'. The court would then have to consider whether you were simply acting as a 'mule' for someone else or if you'd carefully planned to import the drugs yourself (in order to determine whether your role was 'leading', 'significant' or 'lesser'). The table on page 6 then applies.
When looking at that table you need to be aware that the sentences shown there would be reduced for an early guilty plea (by a third in the case of custodial sentences), that sentences of up to two year's imprisonment can be suspended (but higher ones can't be) and that when a custodial sentence is passed the actual time the offender actually spends 'banged up' is a half of the nominal sentence.
You'll see (from the top of page 7) that judges are required to always consider the possibility of a non-custodial sentence, or of a suspended custodial sentence, for Class C offences. So you might, at least, stand a chance of avoiding prison. However, with such a large quantity involved, it would still be wise to pack a bag for your sentencing hearing.