British Car Hire

I am planning to book a rental car from Southampton Central Station, the website says it's Dollar car rental. We are travelling with a toddler and need to reserve a child seat. I am able to select this, but the general description under Extras says "Availability of these extras is not always guaranteed and prices are subject to change". Is it possible the location doesn't provide child seats (which would be a problem for us)?

OK, understood! I just wanted to make sure the option doesn't get shown for all locations, even if they don't have any.

Where exactly is the pick up for this location?

On Google maps this shows as pretty close to the station, but the address and post code locates it in a different place and much further away?

I just checked their website, looks like the office is not as stated on the map, but where the address says. Also, interestingly they say the office is closed on the days I am renting.