Leaking mixer tap in the kitchen sink ?

Hi first time out this season, small drip under sink between the tap and the work surface on my Burstner ventana 500ts , does anyone know how to remove the tap from the work surface ? water dripped under cupbaords onto floor had to disconnect the water while away to stop the water dripping and dry out the van.Back now have removed the sink and reconnect the water we have checked the pipes and they are fitting ok and the water is not coming from the top of the tap so we think there is a seal that has gone but cant get the tap off any ideas would be great can you buy the seals and repair yourself ?