To use the companion you need to buy one of the more expensive fare tickets - these are generally not good value. For example it is possible to buy 2*'Z' bucket UC tickets that it is 1*J bucket
To use the uopgrade award you need to get a Y reward seat - to redeem these you need to phone VS
VS won't tell you how many reward seats they offer - this is commercial in confidence information but rewards will vary for each cabin, for each route and each day. It is well recognised for example that getting a UC reward on the MCO route in the summer holidays is very difficult (popular route not many UC seats) whereas a reward to NYC is 'easier' - more flights per day. Personally I have always got a reward seat when I want one - you do need to be a little flexible though - travel midwekk rather than a weekend, avoid popular holiday times etc.
Miles programmes are very carefully designed by the airlines - for their benefit - but they are designed to encourage long term loyalty.
Spending £25k per annum on the card is a lot of money (well to me it is bt probbaly not to others!) but you need to be flying as well to boost your miles. If you want to be a miles whore consider getting the AMEX gold card which offers (I think) 20k bonus miles in the first year as well as spend miles - collect these and then move them over to VS.