I got all mine sorted through holiday extras last year. Really reasonable prices and very easy to book everything from airport hotels/parking, holiday insurance and added extras in one go.
I booked a room at the LGW North terminal Premier Inn including breakfast and 15 nights parking for cheaper than the exact same parking was on it's own (in laws booked same parking but a different hotel separately!) so definitely worth having a look at the Sleep, Park, Fly deals on the PI website.
Manchester has been quite expensive this year compared to previous years. We need a hotel for 8 September, and with parking, Radisson Blu (who we always choose) want nearly £200! We paid half that last yesr.
Anyway, we usually book direct - we've booked premier inn and the hilton previously. All were fine but RB is our favourite as it's right in the airport next to the terminal.
I always book Radisson Blu too direct through their website. I've never managed to find it cheaper on places like Expedia. It's certainly not the cheapest by some distance, but it cannot be beaten for convenience. Rooms are nice and big family rooms give you two rooms which we love. Parking has always worked well. Very convenient for flights, a three minute walk from hotel reception to Terminal 2. I personally wouldn't stay anywhere else. Nice pool but small. Decent gym. Great spa treatments. Nice restaurant (overpriced mind). Huge buffet breakfast. I've stayed at much cheaper places nearby but for me the cost is worth it.
From Manchester we usually book the travelodge, but it's not there anymore so this year we booked the premier inn with 22 days parking in the jet parks for about £115 which really isn't that bad in my opinion