Negotiations after winning a grant

You want to ask some trusted people in your department whether such a grant would qualify as grounds to renegotiate your contract, as standards for this matter differ widely between universities and departments. Further, what exact grant you won matters much more than the sum - it's ultimately more about the reputation than about the money.

That said, my suspicion is that a 200k grant will not be a reasonable token for any serious renegotiation. While a very nice boost for a young lecturer, such grants are ultimately bread-and-butter for the university, not something that would trigger them to radically rethink your position and rank in the university. Usually, the only grants I see people occasionally use to renegotiate immediately are the top-level personal grants (ERC, or the respective national equivalents) - the type of grants that very few individuals in the entire university get, and which make a dean nervous that you might also get wooed by some other universities to leave and take your grant with you.

The main factor is what the grant covers. If you applied for money to hire a postdoc, then that postdoc would not normally be expected to do any lecturing (under EPSRC rules, for example, and probably most other councils under the UKRI umbrella), so your teaching still needs to be done by somebody and the university is not getting any money towards that. You would then be expected to keep your normal teaching load. If the grant covers, say, 50% of your time for 2 years, then the university gets to keep half of your salary, and can use it to hire a fixed term lecturer. In that case you might be able to negotiate some teaching reduction, although not all universities honour these kinds of buy-outs equally scrupulously.

Even in the second example above, you should not necessarily expect to really have your teaching load halved. For example with grants from UK research councils, the grant actually only covers 85% of what you applied for, and the rest is covered by your institution.

As xLeitix said, ultimately, it is totally OK for a new lecturer to be asking their colleagues carefully worded questions along these lines. If you do not start the conversation with an undue sense of entitlement, then your colleagues will happily help you evaluate the situation correctly, explain the norms at the institution (which can differ from place to place) and draw the right conclusions.