Try eavesway travel, they pick up from Birmingham North hilton pk services m6 or south - hopwood services m42, 01942 727985 - they will take you to the cruise terminal also.
Best way with the least hassle is a taxi to take you there and to bring you back. I would estimate the cost to be in the region of £100 each way but it could be less. The "Airport Taxi" companies are your best bet here but ring around and get a few quotes. The next best way is to drive down, it's about 140 miles so £50 return would cover it plus car parking. The final way is to pay the expenses of a friend to take you and that of course would be twice down and back so £100 plus wear and tear etc. Taxi would be my preferred way as that way there is virtually no hassle and the journey should take just under three hours. ... Regards Neil.
There is an hourly train service direct from Birmingham to Southampton but you then need a taxi to get to the terminal. Have you looked at the dedicated cruiselink coach service operated by Eavesway travel whoc connect with all Princess and P&O sailings. They will take you direct to the ship and once your luggage is on the coach, you don't see it again until it gets delivered to your cabin. They pick up from Hilton Park services (around 10:30) or Hopwood park sevices on M42 around 11am. http://www.eaveswaytravel.com/cruiselink_booking.asp.
Alternative is by car.
It looks as though you might be going on the same cruise as us. Leaving Southampton on 30 August.
We are travelling from Swindon and, by pre booking a train ticket, it is only costing £6 each instead of over £30 by National express!!
Do get in touch if it is this cruise JEANBARNES@sky.com as it looks as though the majority of cruisers will be from USA and Canada, very friendly folk on the internet and we hope to share excursions etc but an English accent would be good occasionally!