Best way to send items via Royal Mail

I currently have a Francotyp Postalia franking machine and it's coming to the end of its contract. Very unhappy with the amount of fees every month/quarter/yearly that is incurred (ie they are invoicing me for a service contract for 2020 when the contract terminates next month!)

Currently we post a few hundred items per day primarily Large Letter 100g/250g using the Mailmark setting.

Can anyone recommend another method of posting (RM OBA or whatever) that is comparable in price to the FP setup and if so how to do so as it seems pretty opaque which leads me to believe that its designed that way to get maximum money out of users.

I use Pitney Bowes franking machine/services and I am equally unimpressed with the "hidden charges" so I fear that no matter what, you will get screwed :-(

Royal Mail steered everyone to Click and Drop. Delivery confirmation (not sure on LL), cheap Zebra thermal printer, no ink costs, free 6x4 labels provided, customs pre-clearance for online orders, no service costs!

Large Letter gets delivery confirmation if you use the CRL code (which is a VAT rate ...so if VAT registered is cheaper than normal 1st/2nd class)
Standard entry pricing to RM OBA is 1000 items a year ... with a few hundred a day, you're into a higher tier for better pricing, and also be good to see what rates you can negotiate for their Tracked 24/48 services, which include daily collections, and full tracking on each item, I know the tiers for that start at 1000 items, and the next tier is 5000 ... as you're at 26000 (100x5x52) a year, it's gonna be good to have a chat with them!

I think I was spending around £18,000 a year with Royal Mail when I first registered, so I get free daily Royal Mail collections. Their business website should tell you the threshold for free collections otherwise it's about £900 ( I think) a year for the them to call at your premises.