Which type of tradesman would I need?

a good qualified plumber can do this for you.

As above or a company that specialise in basement conversions and damp proofing.

If its a stand alone sump pump a plumber can do this. If it is to be used in conjunction with waterproofing a cellar/basement to make it habitable or provide dry storage, then a company specialising in waterproofing should be instructed. It should be noted that damp proofing is for walls above ground and waterproofing is for below ground. If you instruct a damp proofing company, ensure they are also skilled in waterproofing and ideally work should be carried out the BS:8102 ( competent damp proofers will know this British Standard off by heart!!)

As part of a remedial ingress solution this should be dealt with by a damp proofing specialist who may choose to sub-contract the work to a plumber as appropriate.

Yes Plumber will be able to do this if it's a stand alone pump.if however this is needed for converting a cellar/basement then a tanking solution would also have to be undertaken aand conform to British standard.