Assuming no3 is Whilton, I bought Ripple from them, and would offer the following (although this was four years ago)
Their market penetration is huge, for many people it's the first place they look, because they've heard of it. Sorry to offend any brokers here, but that's a fact. A boat at Whilton gets extra exposure just because it's with Whilton
The level of help depends on who you get. When I first emailed interest explaining what I wanted and listing a few boats from their website, I had an email back suggesting that one boat out of my list might not be as suitable as the description sounded and there were also another two boats that on the face of it, fitted my criteria.
I wanted to know the boat was "basically working". A member of staff came out with me, started the engine, put her in gear (she was trapped so couldn't move) and walked me through the boat turning all lights on,, tried the gas (it lit) and ran some water from all the taps, about all I could ask. I then discussed with him whether they would accept an offer below the asking price (stated as being 44k reduced from 48k) he stopped me, went back in to the office, and told me they'd had an instruction that morning to drop it to 38k. So I offered that subject to survey
I couldn't afford more than 40k, and Whilton seemed to stock far more boats below that figure than anyone else
edited to add: unless, like me you wondered around unaccompanied one problem with "prepared for sale" is that it can hide things. I'd be a bit suspicious of a boat that had obviously had a lick of paint just before sale to be honest. I wouldn't buy a boat with a mouldy sandwich in the fridge though, gawd knows what else they've neglected