I've bought my pram, cot and matching furniture from Mothercare recently and had excellent customer service so far. The manager in store was extremely helpful with stock queries (we were being fussy about the colour of the pram) but not pushy. He left us to think about it once he told us the info. The sales people were very polite and did a good job. Delivery was good, the pram came in random different parts over 3 days and I couldn't choose the days. Luckily I arranged to have it delivered to work! The cot/furniture were by DX and I could choose the day.
We've noticed we are missing the guarantee book that should have come with the pram and we've been emailing Mothercare this week. So far they've been very helpful in sorting it out for us. I'll let you know if anything changes!
I really like Mothercare, items are reasonably priced and for me personally, they leave you alone to shop rather than continually asking if you need help that I've experienced in similar shops!