Asda's bras are pretty good and inexpensive.
As far as shapewear goes, my favourite is one that looks like a swimsuit and you wear with your own bra. I wear the size below my normal size (if that makes sense) and you sort of wriggle into it.
I like the Debenhams one best - it's about £35.00. M&S do a similar one, though it's not quite as comfy. Still - I found some M&S ones on Ebay .... new with tags removed and bought several. Some I'm wearing now, and some the next size down. Think those cost me about £13.00 ea on Ebay.