Hi Pussyfoot.
I think you'll be lucky if you can get any recompense from Vauxhall for this. You may be get a contribution if your car has low mileage, full vauxhall service history, serviced at the correct intervals and up to date but they will never foot the bill or acknowledge that it is a common problem.
I used to have a 99 T reg Astra (same shape as yours) and everything but the starter went wrong with it. I have had a look through 'WhatCar' online and in 8 pages of customer reviews no one mentioned the starter fault. However, in parkers, it does mention it in one line in the reliability section:
http://www.parkers.co.uk/cars/reviews/vauxhall /astra-hatchback-1998.aspx?page=4
I wish you the best of luck but I think you are likely to have to foot the bill for this. Make doubly sure it is the starter; check battery connections etc. but it sounds like the starter to me.
Take it to an independent garage rather than the main dealer and you should be able to save some of the cost of this repair as just under �400 seems a little steep to me. While you are having this done consider if doing other work while the car is in bits (i.e. cambelt / water pump) is worth it in the long run - you don't want to get your car fixed and stump up a fortune to have it dismantled again for something else.
Hope this helps, and the very best of luck.