Yep, I have a Silver Cross Sovereign and love it
Got it for the same reasons as you. It easily goes to several different heights. It has 2 trays, and a very small 'safety tray' which always stays in place. She's very secure in it, and as I'm always sitting with her I often don't even strap her in (keeps the straps clean!) and there's now way she could go anywhere.
It is quite bulky but to be honest that's the price you pay for it being comfy. I have since tried her in several different highchairs when feeding out and about, and she hates most of them! Including a cheap Cosatto one, wooden ones, all sorts, so I'm glad I got a decent one.
The Chicco Polly is quite similar, but I personally found it hard to close up. So might be worth having a look at some in Mothercare or similar
Also, keep checking around for offers! I know that Boots online had our highchair for half price a month or so back, I was gutted. Its RRP is £100 I think, we paid £80 as we had a 20% off voucher for Mothercare. Boots had it for £50 bah.