Looks like black alkathene, the tee should have the size written in it, looks like a plasson fitting. I’m not sure speedfit or any other pushfit domestic pipes can be fitted underground, should be blue mdpe.
Edit: if you’re connecting onto lead, there are fittings, unless you want to do away with the lead? A lot of water suppliers do lead ye, replacement schemes, whereby you obtain someone to carry out the leg work from your property to the boundary tap and they’ll connect for free (usually).
Update, OK I fitted the stopcock on the alkathene, it took some red adapter fittings. I turned the stopcock and waited. Read the meter, still moving. Its losing 15 liters per hour. It looks like the lead from the meter is leaking I've read I'm liable to pay the water boards repair costs. Is this true? Are the water Co liable for any of it as its crappy lead with an old style meter, ie no internal spinney thingy.