I need to take a month off for Xmas so want to use a brand in the store. What is comparable to JC? Healthy Choice? Lean Cuisine?

I feel your pain, unfortunately I can't really help you. I do remember reading where the frozen dinners we buy at the grocery store are loaded with sodium which can make you retain water. Hopefully someone else can help you.

You'll want to do a lot of label checking. All of the information is available on the web (I use Daily Plate at Livestrong.com- it's free).

For taste, I'd vote for Lean Cuisine and/or Weight Watchers - I've never been a fan of Healthy Choice.

There are also some less-major brands that are very good and better for you: Kashi, Amy's, Helen's (though I'm mad at them for making a big error on their label), Etchnic Gourmet - though a lot of their entrees are higher in calorie.

you'd be better off doing MOMO following JC guidelines, it has been noted often on the boards that the foods you are asking about are allowed some freedom to be off in calories but to like 100+, also you do no know the portions you are getting in terms of the %protein, carb, fat, where JC is well balanced for nutritional needs, they are also higher in sodium, loaded with too much sauce/gravy for my liking and JC far surpasses in quality/taste. If I need to cut back on my budget I prefer to do MOMO measuring and cooking etc..

You can always steer away from the frozen entrees and plan meals that you cook on your own from basic foods like meat, rice, breads, veggies, etc. I haven't had a frozen entree (except when traveling for business and all I have is a microwave in the hotel) in many months --- nothing "wrong" with them at all honestly and I do use them; however, its not absolutely necessary to eat "out of a box" to stick to the JC model.

If you plan to get the Lean Cuisine types, try the new Healthy Choice (I haven't yet)---these ones are lower in sodium than the other brands. I never liked them much before, but I'm not sure how the new ones are. I am not one to worry too much about exchanges, to be honest --- more on calorie level --- I'd stick to lunches around the 200-250 mark and dinners around the 300-320 mark in calories.

I understand why everyone bashes the store items. They aren't JC food. But.............
I lost 30 lbs on store bought cuisines following JC's guidelines. Just read the labels. They are NOT ALL higher in sodium. Healthy choice has gotten a lot better in taste and they have a HUGE variety. I don't really agree with the claims people make about the calories being so far off. I haven't done any research but I've lost a decent amount of weight eating them.
Following MOMO is a good option that someone mentioned. What ever you do follow the exchange guidelines that JC provides. These store food companies have all their nutrition info on their websites.
Good luck and come back to JC soon.