I echo the sentiments on here that RTM is good, a relatively inexpensive (initially) process and a good way to stop SGIK billing you twice a year for nothing!
Also regarding Chevaliers costs, I would advise waiting for them to take you to LVT before even thinking of paying them. Anyone who never answers the phone, ever, has to be a grade A swindler! He will write to you siting precedent of winning LVT's but he doesn't win them all..... He's isn't that flipping clever or cunning and he can't even spellcheck his correspondence, He's just a thief.
If you're a leaseholder you probably should extend your lease or enfranchise the freehold. Fact. If your lease is approaching 80 years, act now, you save on 'marriage value'. Get a survey done by a local MRICS surveyor who is an expert at freehold valuations. Shouldn't cost more than £500 total. Then you'll have an idea of the cost, it varies from one area to the next don't get a 'desktop valuation' waste of money.
If in January you get a massive bill from SGIK/Hursts:
1. Write to them politely, stating that the works they intend t carry out are over £250 and therefore attract section 21 notice, and that you would like to get your own quotes for work. Stall them asking for 12 months to ascertain the necessity of the works and to get your own quotes, ( I did this) keep questioning them and taking a week or so to write back. Thus avoiding their '21 days to pay or else' B.S. In that time, get Canonbury or
http://www.leaseholddoctors.co.uk/index.html to get you Right to Manage, then start to plan, budget and talk to your neighbours about getting the Freehold! If you are one of many flats this can be very inexpensive! If you one of few flats it's quite pricey, but the advantage is, with a few quid and some neighbourly goodwill you can maintain your own flats under your RTM company.
Whatever you do, dont be intimidated, dont panic and dont worry!
I don't work in property or law and am not an authority on this, but just someone who was fed up of being fleeced by these scoundrels. It's not a particularly complex or difficult problem, SGIK are robbing you, and though it might cost you, you can stop them.